We have a 125 gal. saltwater aquarium, and I love to take pictures of the fish. (but basically, I suck at it.)

I thought that we needed a new camera, but now I'm thinking that I just don't know how to use the one that I have.
It's a Nikon Coolpix 5200.

Can anyone tell me what settings I should go with? Our aquarium has bright lighting. It's 6' long, so the fish do a lot of swimming back, and forth. Some of them move very quickly, while other's will hesitate, for me to get a shot.

Any advice would be greatly appreciated.