[Fishfirst]

Fish stores (especially ones that are still living in the "dark ages" of aquaria aka most fish stores) will have their specific gravity low (around 1.016 -1.018) if your specific gravity is where it is supposed to be (1.025ish) 15-20 minutes of acclimation time may have not been enough especially for clownfish (more sensitive to that kind of stuff because of thier close evolutionary ties to their invertebrate counterpart the anemones) I'm either suspecting acclimation shock, or an aggressive tankmate, or even an aquarist just being a bit over analytical and worried about their fish... clownfish are "weird" and behaive in strange ways sometimes especially when they are new to a tank.