yeh they will ... i have neon tetras that shoaled with black phantoms... so i think they probably will ... aslo cardinal will shoal with neons so i dont see why blacks shouldnt
My neon and WC minnow, *BEFORE* I added 3 more neons, used to hang out with each other, and now the 4 neons (which I just got the last 3 today , they were just newly acclimated) and Oddball shoal together! It looks GREAT! And I'm planning to get 3 more minnows; it'll look even BETTER! ^^;