I just started my tank about 4 months ago and I originally put in 1lb per gallon as instructed by the LFS. I actually put in 90 lbs in a 72 gallon system. Now I've read that I should have at least 4" or less than 1" of sand. I don't want a bare bottom tank so what would be best? Should I take out some to make less than one inch or should I add more sand to make 4 inches? If I take away is there something that I need to do to offset the benefit of the sand? Can I add more sand to an established tank without harming anything?