sorry to here the bad news,but that is to be expected with a gator gar,try to keep him well feed and do not feed live only makes them more aggressive,some times they shred fish and then leave them alone but if you have any thing that you really like I would move it before he ruins it,Mine killed four narrow bar SD and two wide bar SD and a true parrot fish and ate my eight inch Manoguense I tried adding 9 inch red Devil and he is now shredded but the gator stopped going after him that much.I would take it back to were you got because its not the fish they said it was,but I think the short nose gar are still aggressive and might be a problem.If I would do it again I would stick with Florida or spotted gar.good luck hope you work it out,mine I thought was 28 inches but it really was 33 because I thought the tank was4 inches wide when it is actually 28 Inches