my tank is 80 gal. fish only. i have a yellow tang, a blue chromis damsel, and a sleeper goby. just the three fish. i have been trying not to turn the light on as much. i'm using a sandman filter, and a rio powerhead, which are both big enough for the tank. as far as water is concerned, our house is on well water, so i've used that and added salt to it. the tanks has been running nice and clean up until a couple of weeks ago. is the sandman filter a problem? i haven't seen them very often in stores, and don't know of many others who use them. i used to work at an lfs and that is all we used, and they seemed to work great. should i perhaps look into adding a protein skimmer. also i am cutting back on the flake food.