I recently bought a blue hippo tang and notice that its belly is kinda yellow. I already have a totally blue hippo in the other tank and these two look different. Are they the same type of fish or not? Also, this yellow belly hippo tang is hanging around with a pair of large marron clownfish. He sleep with those two together in a big toadstool. The clownfish pair do not seem to mind the tang and the trio alway stay together roaming around the tank. That is kinda odd.