I bought all the materials, to do this, ended up carbon dosing instead, about a year ago. Seen a thread ,about one that was 4' tall. It never continued, for any results.
I will be watching,
I have pondered using ones of these to feed an algae scrubber, extra Co2, and nitrites, from partially anarobicaly decomposed nitrate, and ammonia.
Assuming algae could absorb all the nitrite, ammonia, as fast as bacteria could produce it. It would probably purify 30 gallons a day of 20ppm nitrate water, to 0 ppm. With a 5 gallon bucket sized setup.