Thankz, that was the most informative post so far!
I took the heater outa my 75gal...it is currently 75 degrees...my room is WARM though cuz my other two tankz are 82 degrees at least...so gettin the temp below that might be kinda a hassle. I DO have excellent filtration/current. One Filstar XP3 canister filter (rated for 175gal), two ZooMed Wave Maker PowerHeads (each rated for a 75gal), and one Millenium 3000 (rated for a 60gal tank). The silver dollars have to fight the current in some parts of the tank, so i know there is enough water movement. Got the airlines hooked up to both ZooMed powerheads, so oxygenation is good. Guess all i need to do now is move fish around and get one! 