There are 2 stores in Fitchburg.
All About Animals on the John Fitch hwy next to market basket. They have a pretty good SW section. The fish seem to sell real fast so it's hit or miss as to what they have in stock. They do have corals but I have never bought any from them.
The other store I know of is Port Hole Pets. They are about a mile away just off of the John Fitch, I forget the name of the street but it's the one next to AutoZone. I used to go there but every time I have stopped by lately they have not been open. I had been wondering if they have closed up shop. I hope no animals were left abandoned.