I have started to change all my tanks over to sand. It's easier to maintain, I think it looks nicer and fish love it. My blood red parrot in my 100 gallon hexagon digs in it and throws it around with his fins. Once I have sand in all my tanks that aren't breeding setups I won't ever use gravel again. I agree with putting crushed coral in the filter too. Then it is actually serving a purpose. In my opinion it doesn't really look very nice as a substrate.