I have 2 tanks;both are over 100 gal. One tank has a 350 magnum filter and 2 small side filters. The other tank has a bioball filtration system. That tank has crushed coral in it. The first tank I mentioned has aquarium gravel in it. Both tanks have african cichlids in them. I was thinking of changing the substrate in one or both tanks. Would sand be all right to use in a tank of that size with the africans? I get tired of all of the digging they do in the tanks. I am sure they probably would dig some still, but maybe not as bad? And even though I clean and do reg. water changes, that white crushed coral has a habit of looking stained and dirty. Just curious what you think.