Just a heads up on HYdor brand power heads. I like them and they work fine, but I found that over time, and relatively short period of time, they would sort of set there and pulsate back and forth and never really pump any normal amount of water. I had 7 of them in a period of about 10 months that went south. Hydor usually has a good rep for a decent product. What causes them to do that is if the play in the impeller is restricted and it can not rotate back and forth that small amount on the shaft. I ofund this to come into play with other pumps as well. The pump impeller will rock back and forth becuase its starting against a load (water), and it does not have that "free" rotation to get things going. The motors are relatively weak with little to no starting torque and that back and forth play is what makes the pump to be able to get up to speed and not rock, so pull them apart, and slip the impllers off the shaft and off their adapter, and keep em clean....Before I found this out they were throwing me a lot of curve balls.......