Ok so as you guys know I have 7 Puget garters. Five of them are in a rack system. Two in a twenty gallon aquarium. In order to condense my cleaning time, I'm moving the five into a fifty gallon aquarium. I bought a huge fake grass outside patio mat, and cut out a piece to fit into the aquarium. I was going to use Velcro to keep them from getting under it and making a mess. I can't figure out how to hold it down.

If not Velcro any other idea's on how to keep them from getting under it?

The aquarium is heavy and I'd rather not carry it down the stairs to clean it out every week.