I use tahitian black in my 75 gallon. and have literally hundreds of apples (they breed..alot, I get an egg cluster every 5 days (1 male 3 female adults) the substrate has never seemed to hinder them, and the apples actually outcompete the MTSs and pond snails for food..so much that I have almost no pond snail population outside my fiulter box and my MTS population ahs taken a serious hit.