DC Pump question

[VaReefer]

I did hear back from Coralvue. A check valve is not required, as water return back into the pump will not damage the pump or impeller.

 

[Brad Miller]

A power supply, brushes, magnetism, voltage or any other electrical related issue, wouldn't cause the front drive bushing to seize (if you removed the impeller assy held it in your hand, it was hard to turn, as th OP stated earlier)
And these pumps run on a 0-10 volts input....they can turn very very slow with no ill effects on the unit

 

[Dburr1014]

Is the pump external or internal?