The yellow tang and the panther grouper are actually quite small. I bought the smallest in the store. I would say that the yellow tang is about the same length as my clowns, and the grouper is just a tad bigger. We're probably going to get rid of the grouper soon since he's taking food from the other fish now, and in a couple of months I hope to get a 55gallon. So hopefully by then, the yellow tang won't get too big and we'll be able to get a REALLY small grouper so we can keep him for longer.