So i know cory cats and gravel is not ideal. However, I'm looking for opinions. I have black national geographic gravel in my 20g. It's the 2nd smallest gravel size since the smallest was almost like sand (which I didnt want in this tank). It doesn't seem hard or sharp at all. But I've never kept cory cats, so before I buy them (probably around fall or winter) can I keep them on this gravel? Thanks!