I have these heavy duty 1/2 HP sump pumps that I use for my pond. They sit in a small concrete depression in the bottom of the pond, but the top 3rd of the pump still pokes out above the edge. The intake hole in the bottom is about 2 inches wide. I have never had fish in the pond before, but would like to try it. Will they avoid the bottom of the pump on their own, or should I put something in there to keep them away from it?