A few of you has posted an interest in finding out what pumps ran the coolest without heating up your water. As the summer is upon us, I figured that I would post some results.
The Iwaki external pumps ranked #1 and averaged only a 1 degree rise in temp for a 150 gallon system.
Hydrothruster and little giant were the hottest averaging 4-6 degrees in temp rise.
For internal or submersable pumps, the mag and dolphin pumps rated best. (2-2.5 degree raise in temp)
The rio pumps were the hottest at 3.5-5 degree temperature rise.
Hope this is helpful. As you figured I test everything before using it.
Vic