I have the same problem. Have a 36" wide 30 gallon. 25lbs live rock and some coral frags balanced on the rocks. 2 ocellaris 3 months ago and a recently introduced Yellow Watchman. All seem to be doing great (knock on wood). Just use a Fluval 206 canister, seems to be fine, been doing weekly 5 gallon changes. Was thinking of adding a Helfrich, some kind of useful colorful blenny and maybe a McCoskey. Shied against a 6-line and a grama because was warned of bad behavior from them given the size of my tank.