Algae and Nitrate fluctuation: Big problem or something that will work itself out?

[Rick Garnett]

Cross-posted from /r/aquaponics on reddit

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I am building an aquaponics system with my classes (I am a high school science teacher). First a little history about our newborn system...

Our system is composed of the bottom of a 275 gal IBC with 2 tops of IBCs as media trays filled with hydroton. We began around 01/31. When we started we were lucky enough to be given a 5 gallon bucket of cycled media (including worms) from a local aquaponics grower. We put that in the bottom of the trays and filled the rest with the hydroton and initiated a constant flow. We started with 25 feeder goldfish and one died by swimming too close to the pump, but the rest have survived so far. We started water testing in earnest on 02/02 and have tested daily because I think that would be cool for my students to see something from real life graphed out like this. I wanted high res graphs. I'm pushing for digital probes because that will be awesome to see for the next system we build.

Everything happened exactly how it is supposed to: when ammonia lowered the nitrites spiked, when nitrites came down then nitrates spiked. As I understand it all happened a lot faster because we received that media (was it too fast? See the data below)... Then yesterday on 02/11, the nitrates tanked. Coincidentally, this is the same time we had a bit of an algal bloom. Can the algae suck up that much of the nitrates?

From what I've read, it's nothing to freak about. Everything says just to wait and have patience. Is it going to kill the fish? They started looking sluggish around the same time.

Should I put in an air pump and stones for more DO? Should I just wait it out?

If you want I can provide a view link to a Google spreadsheet of my raw data, but there isn't much of it so far.

Pictures:

• Our whole system [1]

• Left tray (ignore the bamboo, it was an experiment) [2]

• Right tray with parsley and basil to see if they'd droop [3]

• Fish Tank 02/09 [4]

• Fish Tank 02/11 [5]

• Fish Tank 02/12 [6]

• Nutrient table [7]

[George]

The only cure for algae, as I understand it, is to shade the tank.  Plants will remove nitrate.

[Alex Veidel]

Keeping the light from hitting the water will help with the algae, as will lowering the nitrate levels. Like George said, if you have enough plants, they'll lower the nitrates over time.