You will be fine. My sump runs at 12" deep. I have a platform under my Alpha 300 so it sits at about 9" which from my reading seems to be the optimal depth. My 300 kicks some serious butt! I am very impressed with this skimmer after only using it form a month. Also, the red dragon pumps are regarded as the best pumps on the market. As Jeremy said, you should expect no problems with these pumps!
