Just starting my 75G - right now only have the sand in there and the rock is almost done curing. I have 2 Seio 820's in there, one on the left pointing slightly up and one on the back right pointing diagonally to the left (don't want to put on the right side because the tank is visible from the right). The problem is that the sand is getting blown away at the front middle of the tank and piling up on the sides. Any suggestions to keep this from happening. I'm thinking that when I get the rock in there it might be enough to break up the flow enough to prevent this but wanted to ask first. Thanks.