CTU2fan;1694499; said:To be safe I'd always cut my intakes when using sand. Planning to add a large canister (not sure which yet) to my tank and I'll be keeping the the intake a good 8" above the sand. I've got PFS and it's pretty coarse grain, not the fine powdery play/beach sand. The other thing you can do is put a screen over the intakes, I'm playing with that idea but I'm thinking a fine enough mesh to keep sand out will keep the fish poo out or clog anyway.
Canisters shouldn't be affected by sand because of how they're designed; your mechanical media should stop sand. Just means that if you don't cut your intakes short that you're going to need to clean your filter out slightly more regularly.
. I'd stick with the Oscar and con only and if you want to try some dithers then try but I wouldn't do red hook silver dollars. they'll grow much too large for the 90 gallon. regular silver dollars should be ok though just make sure they don't get harrassed by the oscar or con.