Well, these particular growbeds are connected to a 2000g reservoir with cichlids and catfish. I actually do feed an organic pellet, that's actually marketed for aquaculture. Mostly I feed water plants/vegetable and fruits. They get a ton of duckweed, azolla, hyancinth, lettuce, strawberry tops, banana, compost worms and really what ever I have extra of. What I would worry about are fish that have treated by toxic medicines in the past, could enter the food chain. I raise all my own fish, so I know what they have treated with. I don't use dechlorinators either in this tank.