What i have in my 72G tank and works really well for me is 2x Eheim 2217 and the lifestock are angelfish, barbus and plecos. I can handle that bioload maybe just with one but i have double everything in all of my tanks.
haha yeah... it has a thermostat, but i will prolly get one just in case anyway.
opinions on this filter
http://cgi.ebay.com/Internal-Filter...lies?hash=item20acc6aeca&_trksid=p3286.c0.m14
says up to 120 gallons, but...
I'm not a fan of internal filters, but I've heard so-so things about that brand. Probably worth the price.
55 gallon- C-360 canister and a stealth heater to fit the tank
90 gallon- two C-360 canister filters and two heaters that are half the strength, one on each end.