Thank You. You help prove my point. The link to aquarium systems has them all listed as pumps
. The manufacturer would know. Resellers like:
Drs foster & Smith
Have them listed as: powerhead/water pump. Because that's what they are these days--both.
Its easy to find the 400, 600, 900, 1200 series listed both ways.
The Maxijet series 250, 500, 750 and 1000 are/were pumps
The Maxijet series 400, 600, 900 and 1200 are/were powerheads
The 250, 500, 750 and 1000 series--pumps--have become much harder to find over the last few years. Mainly hydropnics and overseas.
My guess is that aquarium systems has improved the impeller and its housing to offer a device that is a powerhead and
Basically, a powerhead just moves water around. Yes, it needs to generate some
pressure, but traditionally--not enough to matter. A pump has the ability to move water against resistance.
If you surf powerheads--they normally don't offer much info in reference to head. Its normally GPH. Pumps usually offer both head and GPH.
Its somewhat ambiguous, but for the most part--pumps are listed as pumps and powerheads as powerheads.