Hi- I am going to be cleaning the gravel in a friends fish tank. THe problem is I am not familiar with this pump/filter. It is a little giant A'quarium series 2 pump model # 2-mdqx-sc The pump is NOT self priming. WHat do I need to do when cleaning the tank(unpluging it & re=priming it) I don't know how it works. Any help would be greatly appreciated. Thanks alot!