I use a 360 gal per hour sump pump in a 40 gal sump feeding a 75gal tank, the pump is one used for outdoor goldfish ponds magnetic rotation, it keeps the tank at 77 F as long as i keep the air in the house at 73 F, these pumps are cheaper than inline piped pumps, but create alot of heat because the entire pump is submerged in the tank, a sump with nice holes cut in the glass with pvc pipe running to sealed shaft external motored electric air cooled pumps add very little if any heat to the water because the water just goes through the pump impellers only and do not pick up heat from the electric motors. I decided to use the cheaper submersible pump so i would not need a heater. but then again leave it up to someone changing the temp setting in the house LOL!.