Cleaning sump with power head or pump

[mikro]

I'm trying to get a power head or a pump to suck out all the stuff in the bottom of my sump. I bought a Penguin Powerhead Model 1140 - 300 gph power head but it won't draw any water out (its ok for circulation in the main tank).
Would someone know of a power head of pump I could use?

 

[dmc888]

I have used my maxijet 1200 for transfering water. Works great.
Rated at 295gph.
Maybe your hose was too long.
I was using 4 feet .
I might be buying another one too.