Oliver, I have a 275 gallon IBC fish tank with something over 1000 Tilapia of various sizes. I have 2 16" deep IBC media grow beds and 1 100 gallon DWC bed. My water #s are very consistent with pH over 7 and ammonia around .25. The beds have red wigglers in them to help break down the solids. I have started adding chelated iron, epsom salt, and potassium sulfate every 2 weeks for plant nutrients. I feed the fish 1 cup of feed twice a day. I have to believe my ratio is far beyond your recommendations. Between the fish tank, sump, dwc, and beds there's about 500-600 gallons of water. Could the answer to why the system works be the amount of food they get (or lack thereof)?