In a small tank like a 29g you might have trouble. Bangaii cardinals are pretty territorial and will often fight among themselves. If they are kept in big groups (20 + fish) then they are fine but when you have 3 or 4 in a tank they will often fight. If you have a pr of Bangaii and a pr of PJ cardinals the PJs might get harassed. You would be better off picking one species only for that size tank. Either a pr of Bangaii or 4-6 PJs.