Well the fish seem to do just fine with it so it can't be that toxic and I can gaurantee you fish are a lot more sensitive to toxins than you are. It isn't meant for plants tho; I read something about too many salts which screws up the EC of your nutrient solution. I'd flush with Flora Kleen or something if you're worried although I read about several people on this website who use aquarium water to water their plants. And if you have access to a hydro website order some ph down/up. Be better than using another thing not made for that and trashing your whole operation.