An 18-year-old tropical fish named Big Blue managed to survive a burglary at Animal Instincts Aquarium & Pet Center in Fall River on Wednesday as one of the burglars smashed a 180-gallon reef tank. Robert Schenck, who owns the store with his wife, Paula, said a group of men broke through the store’s front doors at 12:04 a.m. and stole the registers and computer system, as well as a display of reptile habitats. Schenck said one of the men was seen in a surveillance video using a pipe wrapped in a plastic bag to break the reef tank. Twenty-five tropical fish and 40 corals died, Schenck said. Big Blue, found in a small pool of water, is being dipped into a special solution to clean it and regenerate its natural slime coat, and the staff is hopeful it will survive. Schenck is offering a $750 reward for information leading to an arrest, and said anyone with information can call him at 774-201-1478.