Quote Originally Posted by Blitzjg View Post
Are there clamps I can get to work with that kind of lid? If so what kind?

It's hard to believe they don't sell them with more secure tops
Pet/reptile shops usually sell universal clips. The best kind for a tank IMO are the ones that actually slide onto a track that's on the tank itself, and then lock with a pin. But that is part of the tank, I'm not sure if you can modify it to fit a standard fish tank. I can post a pic if that's unclear.

If you go with a heavy item on top, I'd put 1 on each end of the tank (2 total if that makes sense). I had a friend that used a brick but just put it in the center. His ball was still able to push up the edges (but it was a grown one, so it might be fine in your case).