Frequently Asked Questions


Having trouble trying to build up your nitrifying bacteria?  We recently wrote a blog post called “The Top 10 Reasons Why Your System Isn’t Cycling“.  Hopefully, you can find the answer to your cycling mystery in there!

HOW DO I GET THE WORMS TO GO INTO MY GROW BED?2017-11-13T00:51:12-06:00

First, you need to purchase them from a reliable source. Our worms are drop-shipped directly to you from a USDA inspected and certified facility. Once they arrive you should add them to your grow beds ASAP. They will actually dig themselves in without any help from you! Watch this five minute video to see how I do it.


NO! In fact this rumor is so silly that I wrote an entire blog post on it in October, 2011 titled “Aquaponics and The Wonderful Worm“. Click on the title to read more.


Again the answer is “no”. Worms hate the light, and are happiest in the moist dark of your grow beds. The only time you will see your worms in your grow bed is when you pull out a plant. They will be happily intertwined in the roots taking care of sloughed off dead root material.

DO YOU EVER HAVE TOO MANY WORMS?2019-05-09T11:13:40-06:00

No. Worms regulate their population to match the conditions within their environment and as soon as those conditions no longer support additional aquaponics worms they slow down or stop reproducing.


We have all seen worms crawling out onto the sidewalk after a soaking rain, seemly gasping for air. That they choose exposure to the sun and hungry birds to the water logged soil seems to tell us that worms don’t like soaking wet environments. And what is an aquaponics grow bed if not a soaking wet environment?

The difference with aquaponics worms is that they do not remain constantly full of water, but rather flood, and then drain. This allows for a “drying out” period between soakings that also encourages air circulation within the grow media.

The most important reason why worms thrive within aquaponic systems is oxygen. The reason why those worms crawl from the soil to their death on the sidewalk is not because of the water, but because the water has forced the oxygen out of the soil. In aquaponics, however, not only does the flood and drain action pull oxygen into the grow bed media, but the water that is circulating throughout the system is highly oxygenated. In fact, we have found worms thriving within our sump tanks!

HOW DO I POLLINATE INDOOR PLANTS?2019-03-14T10:10:35-06:00

You actually only need to worry about pollination if you are either growing plants for their fruits and vegetables, or your are saving the seeds from your plants. If you are doing either of these, then you will need to understand which pollination category your plants fall into. This blog post titled Pollination in an Aquaponics System explains further.

See this video for an in-depth tutorial on pollination.

HOW MANY AQUAPONIC PLANTS CAN I GROW?2019-05-09T11:08:30-06:00

That depends on the type of plant you are growing, but in general you can plant about twice as densely in aquaponics as you can in a traditional soil-based garden. This is because your aquaponics plants are getting exactly what they need at the root zone (nutrients, water, oxygen) so the plant doesn’t need to send its roots out searching for these things.  The result is extremely compact, healthy roots and less competition for nutrients and water below “ground”.  Your limiting factor is really how much light is getting to the plant.  Check the space recommendations on the seed packet to get a better idea of how much room your plant will need at the full grow-out size, and know that these spacings were typically made for soil gardens so you can likely plant them closer.  Just keep in mind that airflow/circulation is an important aspect of plant health AND pest control, so give everyone enough room to breathe freely!

Beware of companies selling aquaponics systems that set unrealistic expectations of how much food their systems can grow! Even though aquaponics does generally experience fast growth rates, it is, in the end, still a natural system bounded by natures rules.

CAN I PLANT IN MY SYSTEM RIGHT AWAY?2019-05-09T11:06:37-06:00

Yes, in fact, we recommend that you do in order for your aquaponic plants to become established so that they are ready to take up nitrates when Bacteria Cycling is complete and you have added fish to your system. We also highly recommend adding Maxicrop (or in Australia, this product is called Seasol) to your system during cycling to give your plants an initial boost of nutrients before the bacteria is fully established and the fish waste is providing fertilizer.


In general, any small seeds that you would sow directly into the ground can be sown directly into a media-based aquaponics system. Although with these lightweight seeds it is possible that they will be carried away with the ebb and flow of your water through the pipes, so you may decide to broadcast additional seeds in case a few don’t make it to germination.  We have found that larger seeds that you would directly sow in soil (for example, beans, peas, cucumbers) don’t germinate as well within the media bed. For these we recommend using starter plugs such as Rapid Rooter, Rockwool, or coco coir plugs. See the blog post titled “Starting Plants In, and For, Aquaponics Systems” for more detailed information.


Absolutely. Be sure to wash off as much of the dirt as possible and inspect your plants closely for insects before adding a store-bought plant to your system.

WHAT AQUAPONIC PLANTS CAN I GROW?2019-05-09T11:04:46-06:00

We like to say “anything that grows up grows well in aquaponics”, although that does have a few caveats.  Acidic pH loving plants like blueberries won’t grow well in an aquaponic system because the fish could not tolerate the level of acidity that those plants require.  Also, deep-rooted crops such as corn or wheat likely won’t have enough room to reach maturity in a 1′ deep media bed, so we typically tell folks to leave those large crops in soil outside and use your aquaponic water to fertilize!

Plants in which the edible portions are the leaf (lettuce, kale, chard, mint, and other greens/herbs) will grow faster and with fewer nutrients than fruiting plants.  Plants in which we eat the fruit (tomatoes, strawberries, melons, peppers, etc) will take up more space, time, and nutrients to reach maturity.  We know of people growing papayas, figs, strawberries, heirloom tomatoes, and cantaloupe, and so much more. We have even successfully grown typically “subterranean” aquaponics plants like beets and radishes, although we prefer to grow these root crops within an external wicking bed. Experiment and let us know what works for you!

WHEN DO I ADD PLANTS?2019-05-09T11:03:30-06:00

We recommend adding plants as soon as you have started the aquaponic cycling process. Getting your plants in early gives them time to put down new roots and establish themselves before the fish are introduced and nitrates need to be absorbed. We highly recommend adding MaxiCrop liquid seaweed (about a quart to every 200 – 300 gallons) to your uninhabited fish tank when you plant, this will give the new plants a boost of micronutrients and encourage them to put down healthy new roots. Our Cycling Kits include powdered MaxiCrop and everything else you need to get your aquaponic system cycled quickly.


To raise pH, we recommend using calcium carbonate and potassium carbonate (AquaUp), and either alternating between them or adding equal amounts of each at the same time. We prefer to use these carbonate compounds instead of hydroxide compounds (calcium hydroxide and potassium hydroxide) for several reasons. First, they add to the strength of our buffer. Second, they are not caustic and won’t burn your skin like the hydroxides will. Third, they are on the OMRI list of approved additives for organically certified production.


So what do you do if you need to take the pH down in your aquaponics system? To lower pH we recommend certain acids, such as nitric, muriatic, and phosphoric. Our preference is phosphoric (AquaDown) because it is the safest of the three acids (it is an ingredient in cola drinks) and it adds some phosphate into your system, which your plants will like. That said, phosphates can exacerbate an existing algae problem, so if that is your situation you may want to use one of the other types.

You should absolutely avoid citric acid because it is anti-bacterial. Also avoid vinegar because it is too weak of an acid – you could be pickling your fish before you see the pH results you are looking for.

Rapid changes in pH can be harmful to fish so use sparingly and adjust over several hours or days. Add to system a little at a time, wait for it to distribute throughout the system, then retest pH. Repeat, until the desired pH is reached.

The quantity necessary to lower your pH will vary depending on the nature of the grow media and the carbonate level of the water in your system. To find out how much to use in your system we recommend a technique called titration. Take 1 gallon of water from your tank, figure out how much AquaDown you need to decrease the pH to the target level, and then multiply that by the number of gallons in your system.


Most water comes out of the tap at pH levels above a neutral 7.0. This is because municipalities are concerned about the long-term corrosive effects of acidic water so they adjust accordingly. If your system water comes from a well, you will probably discover the same thing, but in this case, it is the mineral content of the water that is keeping your pH high.

Good news – a slightly high pH is usually not a problem – here’s why. When you start up a new aquaponics system, you “cycle” it. The “Cycling” process is designed to encourage beneficial nitrifying bacteria to take up residence in your system. This process is entirely focused on the bacteria and the fish and, remember, they both prefer a higher pH. This means that water that is a bit above a pH of 7.0 actually helps to get your system “cycled”. Once the nitrogen cycle is fully established, and you have added plants to your system, you will usually see the pH of your system decrease over time. Why? Because the nitrogen cycle actually produces nitric acid which will naturally cause your pH to go down.

But there will be times, especially when your system is young, when you will need to act to push the pH down. And, conversely, over the long run you will regularly need to raise your pH.

WHAT PH SHOULD I TARGET?2019-05-09T10:58:16-06:00

Aquaponic pH management is a bit tricky because there are three living constituencies to consider in an aquaponics ecosystem: Plants, Fish and Bacteria. While the plants generally prefer a slightly acidic pH (5.8-6.2), the fish and bacteria prefer a slightly alkaline pH (7.0-7.6). Therefore, pH management in aquaponics is an exercise in compromise between the two ranges. The ideal target is a pH of 6.8 – 7.0.

WHAT HAPPENS IF I SEE MY BUGS ON MY PLANTS?2017-11-13T00:39:40-06:00

First, you are to be congratulated for your careful observation! One of the first rules of pest management is to be constantly looking out for harmful bugs. Second, identify what bugs you are dealing with. Most bugs (especially aphids) can be eliminated by simply spraying them off with a water jet. If your plants are small you can also try removing them from the media and letting them soak in the fish tank for at least 15 minutes. This drowns the bugs, and the fish get a treat. If neither of these techniques works we recommend an organic insecticidal soap/spray. Avoid any non-organic pest control treatment, as well as organic products containing Neem and Pyrethrum. Both are toxic to fish. And with any spray, no matter how safe, avoid spraying over the fish tank or rafts.

See the post titled “Aquaponics and the Battle of the Bugs: part 2″ in our blog for more detailed information.


Induction lights have many of the same advantages of LED lights. They are energy efficient, the bulb never needs to be replaced, and they have a long warranty. They also run cool and are able to convert up to 95% of the wattage that goes into them into PAR usable light. While they are more expensive than T5 and HID fixtures, they are less expensive than some LEDs, and they also grow plants incredibly well.


BD-platinumLED’s (Light Emitting Diodes) are widely considered to be the future of plant grow lighting. This is because LED manufacturers are achieving better and better control over the spectrum of light that comes out of LED fixtures through fine-tuning the array of LED’s on the panel. LED fixtures are also more energy efficient than HID fixtures, for example, because more of the wattage, or energy, that goes into the fixture is translated into useable PAR light energy. Another nice benefit of LED fixtures is that the bulbs do not need to ever be replaced. In fact, our Black Dog fixtures have a (limited) lifetime warranty.



FLC200D-300x153T5’s, T8’s, T12’s, also known as “linear fluorescents”, are all the long, tube shaped bulbs that we are all familiar with. The bigger the number after the “T” the bigger the bulb. T12’s are the typical “shop light” bulbs and T8’s are what the lighting in most commercial buildings are being converted over to because they are more energy efficient. T5’s are the current standard in grow lighting because they are so thin that you can fit up to four of them per foot of width in a fixture, offering tremendous light intensity.

Compact Fluorescents, or CFLs, pack a maximum amount of T5 grow light tubing into a small space by winding and bending the tube. Lower wattage CFL grow lights, such as 26 and 32 watt, can be used with standard household lighting fixtures, while higher wattage CFLs, such as 125 and 200 watt, require specialized fixtures similar to HID reflectors, but with the ballast included in the hood.


T5 lamps provide the ideal spectrum for plant growth. Photosynthesis rates peak at 435 nm and 680 nm. A 6500K T5 lamp has a spectral distribution with relative intensity peaks at 435 nm and 615 nm. This equates to very little wasted light energy in terms of plant growth. T5 lamps promote incredible health and vigor of seedlings and cuttings. Root development is superior relative to other lighting sources. While T5 lighting is excellent for starting seeds and cuttings, it’s also able to produce enough light for full term growth. Because of their minimal heat output, T5 lamps can be placed 6˝ – 8˝ above the plant canopy which maximizes photosynthetic response. Unlike conventional fluorescents plants grown under T5 lamps do not have to be rotated to the center of the lamp. T5’s slim diameter (vs. T8’s and T12’s), enables better photo-optic control of the emitted light, increasing efficiency in the form of even light distribution.


FLP48-300x190Traditionally, fluorescent lighting was used for seedlings, cuttings and plants with low light-level requirements and HID was used for established plants and plants with higher light-level requirements. Advances in fluorescent lighting technology, however, have provided more options for horticulturists.  T5 fluorescent’s high-light output combined with its low heat and energy consumption makes it an ideal light source to grow a broader array of plants.  Usually, these types of lights are used for seedlings, clones, and some leafy greens where the light can be positioned close to the plants.

PHE400-300x247Frequency output to the lamp and energy conversion from electricity to usable light are the biggest differences between magnetic HID ballasts and electronic ballasts. Magnetic ballasts produce a frequency of 60 Hz. Electronic ballasts vary from manufacturer to manufacturer, but the frequency produced can be 400x that of an magnetic ballast. Magnetic ballasts produce more heat than electronic ballasts, thus making electronic ballasts more efficient at converting electricity into usable light. You will not, however, save money on your electric bill by using electronic ballasts. Since your power bill is based on kilowatt-hours and not efficiency, a 1000 watt electronic ballast will cost you about the same as a 1000 watt magnetic ballast to operate.


Metal Halide (MH) lamps provide more of the blue spectrum, which is ideal for leafy crops, and/or plants that are in a vegetative stage. MH lamps provide a more natural appearance in color and are typically the choice for plants that have little to no natural light available. High Pressure Sodium (HPS) lamps provide more yellow/red spectrum, which is ideal for most plants that are actively fruiting and flowering. In addition, HPS lighting is the choice for growers looking to supplement natural sunlight. Ideally, the horticulturalist will use MH to grow their plants and HPS to fruit and flower their plants.

WHAT IS HID LIGHTING?2019-05-09T10:32:32-06:00

HID lighting stands for High Intensity Discharge, which is a type of light that is one of the more intense (brighter) types of of lighting available. An HID lighting system consists of a ballast, reflector, socket and lamp (light bulb). The ballast acts like the engine, converting and driving energy to illuminate the lamp.

HID lighting options include High Pressure Sodium (HPS), Metal Halide (MH), Mercury Vapor and Low Pressure Sodium. The two typically used for plant growth are HPS and MH systems.

HID systems, specifically 1,000 watt HPS lights have been the standard for greenhouse and indoor lighting for decades.  Only in the past couple of years they have started to be replaced with more efficient and targeted LED lighting systems.


Color Temperature is not how hot the lamp is. Color temperature is the relative whiteness of a piece of tungsten steel heated to that temperature in degrees Kelvin. For example, High Pressure Sodium lamps (HPS) have a warm (red) color temperature of around 2700K as compared to Metal Halide (MH) at 4200K, which has a cool (blue) color temperature. Daylight spectrum bulbs most closely replicate the sun’s temperature at 6500K.

Lumen is a measurement of light output. It refers to the amount of light emitted by one candle that falls on one square foot of surface located at a distance of one foot from the candle. Traditionally, lumens have been the unit of visible light emitted from a source, usually referring to indoor lighting for humans; meaning the brighter the lamp the greater the output. However, studies have shown that a broader color spectrum lamp will perform much better than a lamp with high lumen output, especially when it comes to plant growth.  More commonly, light for horticulture applications is measured in PPFD, or the amount of photosynthetically available light over one square meter per second.


While the sun is the best “grow light” ever invented, only part of the light that comes from the sun is used by plants for photosynthesis. The photosynthetically active radiation (PAR) contains the wavelengths between 400 and 700 nanometers, and falls just within the so-called visible spectrum (380-770nm). The total visible spectrum is perceived by us humans as white light, but with the aid of a prism, we see that the “white” light is actually separated into a spectrum of colors from violet to blue, to green, yellow, orange and red. Plants use the blue to red light as their energy source for photosynthesis.


Being in Colorado, we often think of passive solar greenhouses as great structures for growing in high altitude cold seasonal climate environments. After all a good passive solar greenhouse, like the ones designed by our partners at Ceres Greenhouse Solutions in Boulder, is an excellent way to grow year round with less energy resources than the typical inefficiencies of common greenhouse structures. However, when it comes to growing in Florida, or other traditionally hot and humid climates, the question of whether or not a highly insulated “cold climate” structure is necessary is certainly worth exploring. For a deeper understanding of actual energy utilization please visit the Ceres website to learn more about their greenhouses and energy calculations.


A properly designed and maintained aquaponic system should not produce any foul smells.  When growing fish, you can expect a slight odor, but it should not be offensive.  If you have an effective fish waste solids management system (meaning an adequate bacteria population and/or mechanical solids filtration) you should not expect your system to be very smelly.  A healthy, aerobic (oxygenated) aquaponic system is what we strive for, and will not smell any more than the smell of a healthy soil garden.  Anaerobic zones (oxygen-lacking) within the growbeds, pipes, or other areas of your aquaponic system will cause a foul, sulfur smell.  It will be necessary to unclog any anaerobic zones and possibly add air stones to the area to keep the system healthy and odor-“less”.

Often a dead fish in your tank may be the culprit of a foul smell, so be sure to check in on your fish frequently and ensure that you have easy access to the fish tank.

CAN I GROW OUTDOORS IN THE WINTER?2019-05-09T09:58:47-06:00

There are fish species that can tolerate low temperatures, Koi can manage to overwinter in below freezing temperatures outside.  Tout and Salmon are other species that prefer colder temperatures.  Most other fish species will not survive outside through a freeze, so be sure to check the temperature range of the fish you intend to grow.

Both plants and bacteria cannot survive temperatures around or below freezing (0C – 32F), so growing outdoors through the winter isn’t feasible without a greenhouse to keep extreme temperatures regulated.  Without bacteria, you can expect ammonia levels to build up in your tanks, eventually killing your fish.



Yes! Because fish are cold blooded animals their waste does not, and cannot, contain either of these pathogens. In fact, there was a recent study done by the College of Tropical Agriculture in Hawaii titled “A Preliminary Study of Microbial Water Quality Related to Food Safety in Recirculating Aquaponic Fish and Vegetable Production Systems” that explored this very question and concluded that in general aquaponically grown food is even safer than soil grown food! Click here to read the report of the study findings.


While they are both soilless growing techniques, aquaponics differs from hydroponics in many significant ways. The biggest difference; in aquaponics, the fish provide the nutrients for the plants, where in hydroponics, the plants grow from synthetic nutrients added to the water.  Click here to read our blog post about “12 Ways that Aquaponics and Hydroponics are Different”.

IS AQUAPONICS ORGANIC?2019-05-09T10:15:40-06:00


In fact, it doesn’t work unless it is organic.  The entire system is connected, so trying to fix an issue for one part of your aquaponics system will affect the whole thing.  Adding chemicals, antibiotics, or other artificial additives to your aquaponic fish tank would eventually end up harming your plants. If you use pesticides or growth stimulants to aid your plants, it will harm your sensitive fish.  Every element that you add to your system must be plant-safe, fish-safe, and definitely nothing that’s anti-bacterial!

In terms of official USDA Organic Certification, commercial aquaponic farm are eligible to be certified.  There are strict standards that farm managers must follow, which regulate nutrient additions, pesticide use, food safety, and other aspects of farm operations.  For more information, reach out to your local organic inspector.



There are many benefits to growing your food with aquaponics. Remember that aqua stands for aquaculture – raising fish. Ponics – in Latin means to work. Hence, you are putting your fish to work, growing plants!  Here are some of the benefits of growing with aquaponics.

  • Aquaponics is Sustainable – From efficiently using precious water resources, to producing no waste, aquaponics is sustainable in so many ways.  Check out our blog, “7 Ways Aquaponics is Sustainable” for the full run down.
  • Aquaponics can be used anywhere –  While soil is immensely valuable in growing gardens, there are places which have very poor soil or no soil at all. Sand, heavy clay, asphalt or concrete, soil contaminants or rocky terrain make it difficult if not impossible to grow. Aquaponics, however, allows growing in a wide variety of places. It can be built on parking lots, rooftops, backyards and basements. It allows for growing indoors or outdoors. In addition, Aquaponics can grow year-round where ever you can control the temperatures. Here are some of the benefits of growing with aquaponics.
  • Aquaponic is local – It doesn’t get any more local than growing food in your home, school, or small community farm. Most food travels thousands of miles to get to our plates and by the time it arrives it has lost much of its nutritional value.  Why not grow more of our produce and protein locally to help the environment.
  • Aquaponics is Organic – Growing your own vegetables, fruits and herbs will provide you the most nutrient dense food possible. Aquaponics is a natural ecosystem without any harmful chemical fertilizers and pesticides used in commercial agriculture. Feel confident that you know exactly what’s in the food you’re eating because you grew it yourself!
  • Food Security – Food independence and security is increasingly important in these changing times.  Aquaponics is one way of living a more self-reliant lifestyle. By adding in solar powered systems and energy-conserving building practices,  we can start to see the possibility for everyone to grow their own food.

Pet and Aquarium Stores: Just about any fresh water aquarium fish from a pet store works well as an aquaponics fish. Pay special attention to the temperature range that the fish thrives in, and whether they would be compatible with the other fish in your tank (i.e. not eat them). If your system is very small you might be able to stock your tank simply by visiting your local pet store. Pet store fish we have grown with success in aquaponics so far are goldfish (avoid feeder goldfish, they are prone to disease), koi, oscars, pacu, and guppies.

Hatcheries: More and more fish hatcheries are willing to sell small batches of fish to local aquaponic growers. If you have a hatchery nearby that is willing to sell to you this is a great option if you plan to grow fish to eat.

Online: You can look for local or national fisheries online and order many species through the web to arrive via mail.  Please note that live fish are shipped with a limited oxygen supply, so make sure to receive them as soon as they arrive to ensure they don’t stress in extreme oxygen or temperature situations.  Specific species may be prohibited in your area, so please be sure to check with your local regulations before ordering.

IS THERE AN ORGANIC FISH FEED?2019-05-09T10:22:00-06:00

Yes! And we are proud to be the first company in the country to offer it! Our AquaOrganic feed is free of fish meal, GMO’s and soy.  It is the only fish food available that is USDA Certified Organic.

Learn more about our organic fish feed production in our blog post USDA Certified Organic Fish Food Partnership with Industry Leading Aquaponics Experts 

WHAT DO I FEED MY AQUAPONICS FISH?2019-05-09T10:23:10-06:00

Depends on what type they are. Carnivorous (examples – trout, perch, and bass) require a feed that has high levels of protein (45 – 50%). Omnivorous fish (examples – tilapia, bluegill, koi, and catfish) require a lower protein feed (typically 32% protein). Younger fish require more protein than mature fish.

While we applaud the efforts of those who try to further “close the loop” by producing their own feed (such as cultivating their own Black Soldier Fly larvae, red worms, and duckweed) we still strongly recommend that you feed your fish a professionally formulated feed. This will ensure that not only do these fish that are in your care receive an optimal diet for their health but that your plants also get a balanced diet through their waste. Please read our post titled “Aquaponic Fish are Not Garbage Disposals!” to learn more.

HOW MUCH DO I FEED MY FISH?2019-04-14T17:47:58-06:00

In an aquaponic system, the fish feed one of the most important inputs.  There is a direct relationship between the feed going into the system and the growth of your plants.  Think about it: You add feed into the system, the fish eat the feed and produce ammonia, bacteria convert ammonia into nitrates, the plants consume the nitrates and grow.  Because of this relationship, balancing the proper amount of feed entering the system is essential to the overall success of the system.  When sizing an aquaponic system, you can use the formula, 20 g of feed per square meter of Deep Water Culture growing area.  Using this formula, you can calculate the amount of feed needed in your system.

Only feed the fish what they will consume in 5 minutes – scoop out any uneaten fish food to avoid unwanted water quality issues.  If your aquaponic fish don’t seem to be hungry don’t feed them. Fish can survive for weeks without feeding.

If you are cycling your system with fish, feeding should be kept to an absolute minimum during the first 1-2 months.  Once your nitrifying bacteria levels can quickly digest ammonia and nitrites in your system, increase feeding levels, again paying attention to how much the fish consume in 5 minutes. We prefer to feed our fish 2-3 times per day, to encourage a steady metabolic digestion rate and maintain a steady amount of solids. As a guideline, mature tilapia typically consume about 1% of their body weight in feed a day, while fingerlings can consume as much as 7%.

CAN I PUT FISH IN MY SYSTEM RIGHT AWAY?2019-03-14T09:38:39-06:00

Yes, we like to refer to this as “Fish Cycling,” meaning you will be monitoring the health of your fish population while simultaneously growing the nitrifying bacteria population.  Adding the fish before the bacteria does come with some additional challenges, so see our post on Cycling With Fish for special considerations when doing this.


In a smaller sized tank, <50 gallons of water, we recommend stocking the tank with 1″ of fish for every 1 gallon of water.  For example, a 10-gallon tank could hold 10x 1″ fish or 5x 2″ fish.

For larger fish in tanks over 50 gallons, we recommend a stocking density of 1 lb of fish per 5 -10 gallons of water, or 1-2 fish per 10 gallons of water. Do not stock more than 1 pound of fish for every three gallons of water, this will greatly increase the potential for fish stress, fish diseases, and an overall imbalance of your aquaponic system.  Learn more about fish stocking density in our blog, “Aquaponic Fish Production and Stocking Densities”.


fish-eating-goldfishIn aquaponic systems, you can grow any freshwater fish that appeals to you.  You will want to consider natural environment that the fish species comes from to ensure that your aquaponic system can  provide a similar environment. Trout, for example, like water temperatures below 65 degrees. Can your environment consistently provide this? If you are mixing fish species together in the same tank, be sure that they have similar living requirements. Do they all prefer the same water temperature, eat the same food, and have the same oxygen requirements?

Don’t mix carnivorous fish with herbivores, or you will find that you are just providing an expensive meal for your carnivores!  We have found that tilapia, other cichlids such as oscars, pacu, goldfish, and koi all co-exist well together in an aquaponics system.


We recently wrote a blog post called “The Top 10 Reasons Why Your System Isn’t Cycling“.  This blog covers all the reasons your system may not be cycling and what to do about it.  Hopefully you can find the answer to your cycling mystery in there!

CAN I SPEED UP AQUAPONICS CYCLING?2019-04-14T17:24:35-06:00

Unfortunately, nitrifying bacteria are some of the slowest growing bacteria in nature, and the cycling process can take as long as six weeks. There are a few things you can do to speed up this process, however.

Temperature – like most microorganisms, nitrifying bacteria multiply more quickly in warmer conditions. Their optimal temperature is between 77-86°F (25-30°C). If possible, try to keep water temperature within this range while startup cycling.  At 64°F (18°C) their growth rates decrease by 50%. At 46-50°F (8-10 °C) it decreases by 75%, and stops all together at 39°F (4°C). It will die off at or below 32°F (0°C) and at or above 120°F (49°C).

pH – Bacteria prefer a pH range between 7 – 8. Use aquaponic pH up and down products to keep your pH in this range during cycling.

Oxygen – Nitrifying bacteria are aerobic and will multiply much faster under highly oxygenated conditions. Even if you are cycling without fish be sure to have as much oxygen in your tank water as you would if the fish were there. Think of the bacteria as just another living organism that requires oxygen in your system.

Adding bacteria – You can “jump start” the process by adding bacteria from an existing colony. Good sources of beneficial bacteria are ranked here, leading with the best (the lower you go on the list the more chance you have of introducing a disease into your system):

  1. Microbe Lift Nitrifying Bacteria product (included with the AquaCycle Cycling Kits)
  2. Media from an existing aquaponic system.
  3. Filter material (sponge, biomedia, brushes, mats, etc.) from an established, disease-free aquarium.
  4. Gravel from an established, disease-free tank (Many local pet and aquarium stores will give this away if asked.).
  5. Other ornaments (driftwood, rocks, etc.) from an established aquarium.
  6. Squeezings from a filter sponge (any pet and aquarium store should be willing to do this…).
  7. Rocks from a backyard pond with fish in it.
  8. Rocks from a river, lake or wild pond.
HOW DO I CYCLE WITHOUT FISH?2019-04-14T17:17:22-06:00

There are several ways to add ammonia to your system, but honestly, the best is to simply purchase our Cycling Kits. They come in 3 sizes – Small (< 100 gallons), Medium (100 – 300 gallons) and Large (300 – 500 gallons). They come with all the ammonia you will need to fully cycle the corresponding size tank, powdered seaweed to provide a rich supply of micronutrients to get your plants off to a great start, and detailed instructions.

With Fishless Cycling you can safely add fish to your aquaponic system after your ammonia and nitrite levels drop to zero, or close to it, and you have measurable levels of nitrates. This tells you that both the ammonia converting bacteria (nitrosomonas) and the nitrite converting bacteria (nitrospira) have become fully established and are ready to efficiently process fish waste.

HOW DO I START THE CYCLING PROCESS?2019-04-14T17:14:45-06:00

Once you have your aquaponic system set up and your test kit in hand all you need to do to start the cycling process is add a source of ammonia. Traditionally this has been by adding fish and using the ammonia from their waste, but we’re not a big fan of using fish as an ammonia source. Without nitrifying bacteria established in the system, the rising ammonia and nitrite levels may exceed toxic levels for your fish.  Instead, we prefer a technique called “Fishless Cycling” where an external source of ammonia is added to your aquaponics system to establish nitrifying bacteria before your fish arrive in the tank. Why is this?

First, both you and your fish will likely experience much less stress because you will not be worrying about your fish health through the nitrifying process. Second, you can more precisely control how much ammonia is added to your system during cycling. For example, if you see that your ammonia level is creeping up to 8 ppm, but no nitrites have shown up yet, just stop adding ammonia for a few days and let the bacteria catch up. You can’t do this with fish, as 8ppm of ammonia will surely kill them!

The practical result is that with Fishless Cycling you can fully stock your tank once cycling is complete, versus gradually increasing your stocking levels as is recommended when cycling with fish. This is especially beneficial to those who are growing aggressive or carnivorous fish because they are less likely to attack each other if they are all introduced to the tank at the same time.

WHY DO I NEED TESTING TOOLS?2019-04-14T17:02:13-06:00

Without being able to see nitrifying bacteria grow, you must have some way of telling where you are in the aquaponics cycling process – typically a four to six-week endeavor. Specifically, you must monitor ammonia, nitrite, and nitrate levels as well as pH so that you know that all these elements are within a target range. If they are not, you may need to take corrective action. This is also the only way that you will know when you are fully cycled and ready to add your fish. Plus, watching the daily progress of the cycling process is fascinating and something you can only see through the lens of a test kit. By the way, once you reach the point that your system is fully cycled, you will need to do much less monitoring than during the cycling process. So get through the cycling process and look forward to reaping the fruits (or should we say the “fish”) of your labor.

To do the testing, most aquaponic gardeners use a product by Aquarium Pharmaceuticals Inc. called the API Freshwater Master Test Kit. This kit is easy to use, is inexpensive, and is designed for monitoring the cycling process in fish systems.  That’s why we sell this kit in our shop!

You will also need a submersible thermometer to measure your water temperature. Temperature affects both the cycling rate and the health of your fish and plants once you are up and running.


Nitrogen cycling happens in soil and water all around the earth. Aquaponics cycling is the natural process of bacteria oxidizing ammonia into nirates.


Cycling Process

The cycling process starts when ammonia is present in your aquaponic system. Ammonia (chemical formula NH3) is a compound made of nitrogen and hydrogen. Fish produce ammonia in the form of feces, urine, but mostly from respiration in the gills. You can also add pure ammonia in liquid or powder form. Just as our own waste is toxic to us, ammonia is toxic to fish and can kill them, and is not available as a nutrient for uptake by plants. The cycling process converts ammonia to a less toxic form of nitrogen  (nitrate) that plants can readily digest.

Ammonia attracts nitrosomonas, the first of the two types of nitrifying bacteria that will populate the surfaces of your system. The nitrosomonas bacteria convert the ammonia into nitrites (NO2). This is the first step in the aquaponics cycling process. Unfortunately, nitrites are even more toxic than ammonia! But the cycling process does not stop there. Nitrites attract the bacteria species nitrospiraNitrospira converts the nitrites into nitrates. Nitrates are generally harmless to the fish and an essential nutrient for your plants.

Cycling Startup

Cycling starts when first setting up or restarting an aquaponic system. The cycling process generally takes from 4-6 weeks. The time frame is dependent on the water temperature (ideally 75° – 80° F or 24° to 26° C). Water temperatures outside this range will take longer to cycle since the bacteria will be slower to eat and reproduce. Once cycling is complete, water temperatures should be between 70° to 75° F, 21° to 24° C). This is a temperature range that is good for both fish and plants.

You can speed up the cycling process by introducing nitrifying bacteria instead of waiting for them to appear on their own. Add a bacteria supplement to the media surface or water, so they can populate your aquaponic system faster.

The Aquaponic cycling process
Nitrification Cycle Chart


Fish Cycling

  1. Stat fish cycling by adding fish to the water. The fish will provide the ammonia source. Do not feed the fish for the first 24 hours.  Only lightly feed for the first several days.
  2. Add a bacteria starter or let the bacteria populate naturally.
  3. Perform a water test every day to check ammonia, nitrite, and nitrate levels. Ammonia should remain below 3.0 ppm. Nitrites should remain below 1.0 ppm. Nitrates will increase over time.
  4. Exchange 1/3 of the tank water if ammonia gets above 3.0ppm, or nitrites above 1.0ppm. Fish can suffer and may die if levels get higher than these.

Fishless Cycling

Cycling with fish can be stressful (on both you and the fish). An alternative is fishless cycling.

  1. Add a bacteria starter or let the bacteria arrive naturally.
  2. Add a supply of ammonia (powder or liquid) until levels are at 4.0 ppm.
  3. Perform water tests to detect ammonia, nitrite and nitrate levels.
  4. Continue to add ammonia to keep the ammonia level around 4.o ppm.
  5. Cycling is complete when ammonia and nitrite levels drop below 0.5 ppm with 24 hours. The presence of nitrates indicates cycling is taking place.
  6. Stop dosing the system with ammonia and add your fish into the system.  Do not feed for the first 24 hours.

Common Cycling Mistake

A common mistake is to add bacteria starter and ammonia only in the beginning. When a water test shows 0 – 0.5ppm ammonia, it is assumed the system is cycled. Really this means its time to add more ammonia. The ammonia needs to be available constantly for the bacteria to thrive. Another mistake is to add ammonia and have fish. Only one source of ammonia is necessary, and fish produce ammonia on their own. Adding ammonia supplement with fish in the tank is bad for their health.

Cycling is complete when a water test detects nitrate levels increasing. At the same time, ammonia and nitrite concentrations are consistently below .5 ppm or less. Your system will be fully cycled making the water safer for the fish and nitrogen available for the plants. Once the nitrification cycle starts, it will continue until the source of ammonia is removed or temperatures rise or fall dramatically.

You are a bacteria farmer. It is just as important to keep your bacteria happy as your fish and plants. Nitrifying bacteria are essential to the health of your aquaponic system. Nitrification happens all over the world. This is just one of the ways that your aquaponic system mimics a natural ecosystem.


Here is what we recommend.

1) Get an API GH and KH Test Kit and figure out what your carbonate levels are.

2) If you are above 4 dKH, then you should be fine for now but be sure to retest weekly as part of your normal testing regime. Remember that as your system matures, it will create more and more nitric acid so your KH levels will drop over time.

3) As you approach a dKH of 4 or lower, we recommend adding potassium bi-carbonate (AquaBuffer) to your system at a rate of 2 ½ teaspoons (12 ml) per 100 gallons of system water for each dKH level you need to go up.


There are a few critical reasons. First, while fish can generally adapt to pH levels that are outside of their ideal range, they cannot handle dramatic, rapid swings in pH. We take phone calls every week from customers who are struggling with what appear to be random fish deaths. When we ask them to measure their pH several times during the day, we often see dangerous intra-day swings of an entire point or more! We then ask them to test the KH levels in their water and they nearly always report that they have a dKH that is below 4.0.

Second, maintaining a buffer is critical for bacterial health. If you get to the point where your system carbonates are completely depleted, your system pH can “crash” (decrease rapidly). If it does, your beneficial bacteria will quickly die and biological filtration will stop entirely.

Third, if you don’t have at least a minimal buffer of 4 dKH established in your system, you will need to manage pH on at least a daily basis (i.e. measure it and adjust as needed). If there is no buffer to offset the nitric acid in your system it will simply lower your pH, unimpeded. So not only is a lack of carbonates dangerous to your fish and bacteria, but it will also create a maintenance nightmare for you!


At The Aquaponic Source we help customers with questions and concerns about pH each and every day. Generally, the questions fall into one of two categories:

“The water out of my tap is a pH of 8 (or more) and I can’t seem to lower it reliably. What should I do?”
“The pH in my system is dropping constantly and I have to add something to raise it almost daily. Is this normal?”
Most pH mysteries in aquaponic systems boil down to how “hard” your water is that you put into your system. This “hardness” dictates the buffering capacity of water. Let me explain.

Water from most sources has some level of mineral salts dissolved in it (purified water such as distilled or RO filtered [reverse osmosis] are clear exceptions). Among these dissolved salts are certain specific minerals that strongly affect the pH of your water. The concentration of these minerals in your water is often described by the term “hardness” – the higher the concentration of these minerals, the “harder” your water is. There are two types of hardness in water – “carbonate hardness” (KH), which is sometimes also referred to as the water’s “buffering capacity” or “alkalinity” (not to be confused with an “alkaline” solution which would have a pH of greater than 7) and “general hardness” (GH) which refers to the concentration of calcium and magnesium ions in the water.

The general hardness of the water affects pH but it is the buffering capacity (KH) of your water that is the more critical pH factor. This buffering capacity acts like an invisible sponge that soaks up whatever acid or base is in your system – or that you add to your system – until the capacity of the buffer is “used up”. With this sponge-like behavior in mind, imagine trying to adjust your pH. Let’s say you have a pH of 8.0 in your aquaponics system and you would like to bring it down to 7.0. You start adding an acid…and adding…and adding…and little or nothing changes. And then all of a sudden the pH plummets. What has happened? You had a strong buffer (meaning there was a lot of KH) in your system which you eventually “overwhelmed”. Another way of thinking about this is that you “filled up” the sponge.

You can actually measure your KH level using an API GH and KH Test Kit. The larger the KH number, the more resistant your system will be to attempts to alter pH. Having a higher KH level can be beneficial in a fully cycled system because, as you will recall, the nitrification process produces nitric acid which will persistently drive pH down in an unbuffered environment. A rule of thumb is that a KH of less than 4 dKH (“dissolved carbonate hardness”) means that you don’t have much buffering capacity and you may see rapid, frequent swings in pH.