depends most on what type of africans you are gonna get. some smaller mbuna, or large haps?? if you go the smaller mbuna option, 30 ish would be possible. i have a 90g with a 55g sump, holds about 40g of watter and i currently have 38 ish in there, 16-18 demasoni, 10 sp. orange caps, and 5 perlmutts with 7 more comming in a few weeks. after they grow im going to add some yellow labs i have as well. but if your going big, large haps like venustus, or something from another lake like fronts (which i wouldnt recommend) you cut the number down drastically.