HI John, I recently bought a Blue-spotted Watchman Goby. It is very beautiful however some of its fins are frayed and torn. Hello again Ryan, Fin injuries are fairly common in captive marine fish. In reef aquariums it's possible for some invertebrates to cause fin injuries, crabs and shrimps being the likely culprits. Parasitic and bacterial infections can give fins a torn or frayed look as well.
Healthy fish have amazing healing and regenerative capabilities.
It is not unusual for fins that are simply split to heal completely in a few days. The mend starts at the base and gradually closes towards the perimeter, like a zipper. When portions of fins are taken off the process takes longer. In this case the fish must regenerate both the fin tissue and the rays that support it. In some instances the fish does not regenerate the missing portion, or only partially.