by Joanne Bell, Grow Lab Manager, The Aquaponic Source
We had an unfortunate invasion of planktonic algae (floating microscopic plants) in one of our grow lab systems. Unlike other forms of algae that cling to surfaces, this type is free-floating in the water. In lakes and ponds, some planktonic algae is considered beneficial. But too much can deplete oxygen and kill fish, according to Texas A&M’s Agrilife Extension.
Since, planktonic algae feeds on nitrates, it “bloomed” within days making it look as if pea soup were running through our system. A similar bloom in a tabletop aquaponic system appeared to cause the loss of a goldfish, so we didn’t want to take any chances with our tilapia and bass. Not to mention, depleted oxygen levels could alter future test results.
We discussed our options: bleach the system or run a UV sterilizer. Both would eliminate the algae (and the beneficial bacteria). UV sterilization would also deplete boron, manganese and iron. (Howard M. Resh, PhD, Hydroponic Food Production, 2001) But, bleaching the system is very labor-intensive. So, we settled on the lesser of the two evils: adding a UV sterilizer to our aquaponics system.
As expected, the water became crystal clear within 2 weeks, at the same time the plants began to show symptoms of nutrient deficiencies.
We thought you’d like to see the impact of UV sterilization-induced nutrient deficiencies on plants. It was most apparent in our tomato plants.
Tomato plants in system w/ UV sterilizer
(Note growth habit: tall and stringy, discolored and curling leaves.)
Upper leaves. (Note: curling and discoloration.)
Tomatoes in system w/o UV sterilizer.
(Note: healthy green, compact, bushy plant.)
Lower leaves. (Note: less curling.)
How many hours per day / week did you have the light on ?
In our system at the office we run them for 18 hours a day. In June when power prices go up we will drop it down to 14.
What if you run the UV in the sump so the fish waste water sees the plants first? With enough flow wouldn’t all the water clarify?
Since a large portion of nitrifying bacteria exists in the water column we generally don’t use UV sterilizers except with special cases, quarantine tanks, and finishing tanks. When we do use them we put them after a filter, without a filter definitely after the media beds.
The solution is simple, by empiric research, u can reach the point where u can dosing em micro nutrient on weekly / monthly basis while still use UV filtration, so the boron, manganese n iron still there, cos I just more benefit with uv filtration in a long basis rather than not use it, make any sense? Cos in long term, fungus, and bad bacteria always show somehow in the system, very frustrating
Hello, We rarely spec UV filters in our systems. With a good filtration system, it’s rarely needed. We agree on the micronutrients. We add them to our system here in the lab and have had increased growth, reduced pests, and much better-looking plants in general. Thank you for your input.
What’s up friends, how is all, and what you want to say regarding
this paragraph, in my view its in fact amazing designed for me.