I like to use crushed coral for my cichlid tanks to keep the pH up and cover it with gravel or sand to prevent catfish from being injured on the sharp coral. If you are not going to keep catfish then the crushed coral is fine. My cichlids have never missed a sandy bottom. I tried sand for a while but they are such strong swimmers that they kick up the sand into the water column and this wears out your filters faster (the impellers). I would go with gravel if you want the longest service out of your equipment. On the other hand the sand made my tank look great! You can also just use regular type gravel as well. I use the crushed coral to boost my pH because our water source here has just above a 6pH.