Florida Gar ID and questions.

I just bought my first gar and wondering if you guys can confirm for me that it is indeed a Florida Gar?!
I've been looking for one for a while and the one I finally found was a little bigger than I had hoped (12"). I couldn't help my self and bought him. I'm new to gars and a little concerned he might eat my other fish. I have in the tank with him: 5 3-4" silver dollars, 5-6" Lima shovel nose, 5 " Four lined pictus, 5" Asian bumble bee cat. Should I be okay or will he go after my fish??
By the way its a 300 gallon tank 96" X 30" X 25"

Thanks!

Anyone??

Thanks. I must have an aggressive one.. I just got home and several of my silver dollars have bite marks on their backs and it seems its a matter of time till he gets one. My LFS offered to take him back, so I think im going that route.
Im going to try to get a smaller one in the future