I have a very small system and the pump is in the water inside. I guess it depends on how big of a system you are planning. I have seen many with big pumps, like well pumps doing huge sytems. Mines a 130 GPH and most cloners are 256 GPH. They don't add much to water temp. I also have AC the room is about 75 to 80 degrees and the rez 68 on the floor.