Poor Marlin

Sadly, Marlin didn't last the night. Later in the evening we noticed white smudges on him in the black-light that I hadn't noticed in regular light, he looked bruised and beat up. By the time we went to bed he was gone, and poor Nemo was back to swimming sadly in the far back of the tank.  I'm going to take him back to the pet store and complain, but I'm fairly sure they won't refund/exchange.  In the tank Nemo and Marlin came from, there was an "overactive and hyper" (as the sales lady put it) sleeper goby, perhaps he had been beating on Marlin.  Our tank's salinity was spot on, the temperature was perfect, nitrates are good, so the only reason I can see is he came to us sick and or beat up.  It was a sad night, after seeing the change in Nemo when we added Marlin to the tank, only to have him go back to his lonely swimming.