4 is a pretty safe number comfortably. I'd say 4-8 with the right filtration. Two things, 1) it will take your peacock bass quite a while to hit the 2ft mark if you're starting with small ones, 2) the types of shovelnose catfish and quantity greatly varies depending on what species you are talking about keeping. Those dimensions would be fine for Lima's, Juruense, and Tigrinus species for life. If your talking TSN, Planiceps, or hybrid RTCxTSN then it would be to small. The 36" width is key to housing the shovelnose long term whatever kind you chose and for 2ft peas as well ~Trent