I wanted to do tilapia but they are only available mail order. I ended up buying 25 catfish along with a pound of minnows. I lost most of the catfish and will replace them next month. So right now I have 2 or 3 catfish plus hundreds of minnows.
I guess the minnows are responsible for the bulk of the nitrates at this point.
It's really exciting to see the symbiotic relationship here. The fish produce the nitrates (which is toxic to them). The plants use the nitrates as fertilizer and return the clean water, free of nitrates, back to the tank below. The rapid growth of the plants is a powerful testament to the strength of this idea!
