Are QTing? if so then the clowns should have ben QT
for 3-4 weeks and then added to the display. Then Id wait at least another 3-4 weeks if not more before you add the Cardinal that will allow him the proper (recommended) QT
period as well as allow for you bacteria (in the display) to catch up with the new bio load of the clowns. personal if it were I, I would take it as slow as possible no reason to rush into it. Rushing will not benefit the tank the only thing it might do is burn a hole in your pocket...