I had the same problem when I added one to my 55 gallon community. I left the lid propped the best I could. It eventually aggravated me enough thought that I did a large water change and pulled the tank out another inch. I didn't have any issues with the lid propped though. Just be careful to make sure that when you say you pushed it down a little, the filter is running level... it does have the little lever on the bottom that keeps it at the right angle; if that gets partially off kilter it can collapse and splash some water out.