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.
this was very helpful 🙂
No matter how much acid I add ph will not go down
I have a home system that had the same issue. I learned it was part of the “hardness” of my water. Here is a post that might give you more insight in to your challenge.
What if you’ve already used citric acid? How do you counteract it?
I would recommend testing your ph, ammonia, nitrite and nitrate levels right away to help determine if you have killed off your nitrifying bacteria. If you are seeing high ammonia and/or nitrite then you should perform a partial water exchange to help reduce levels so your fish are not at risk. You can also reduce feed for a day or two. I would then purchase some Nite-Out to help re-establish your bacterial colony. Our ph Down would be your best choice in the future for lowering pH but I’m not sure your need to lower your pH until we see your most recent test results. You can send them to me directly at email@example.com
Ok im gonna get jazz about this question, we have a Aquaponic/hydroponic store here in Austin, I called to see if the had other options for lower ph other than Muriatic acid and they Suggested Earth Juice “Crystal pH Down” which on my part didn’t look at what it was made from. 100% Citric acid. Guy told me it was Safe on the fish don’t didn’t even think to read ingredients.
With it being called a Crystal pH Down did it go through a process to be non lethal to Bacteria or did he just sell me what needs to move off the shelves?. Thanks in Advance & High5
Good catch Thomas. Citric acid is not recommended due to its anti-bacterial properties. I checked with the Earth Juice website and didn’t find anything that said it was a fish safe product. I wouldn’t use it in my system. Thanks for the High 5 and the question.