37g tank.. Growing everyday but..

[Catica405]

I have a 37 gallon saltwater tank, water parameters are good ammonia zero, phosphates at 0.3, nitrates are 10 or less I have two tomato clown fish and two fire fish. I also have a twin spot goby in there doing really well I was wondering how many more fish can I add to my tank with the making it look crowded. I have also noticed a bit of fin rot? The Goby had it for a while as he seemed to be sick for a couple days. How can I treat this? I'm posting some pictures.
Also the female clown has been giving the male a hard time, is this normal for matted pairs?

 

[sir_dudeguy]

As for the clowns... Completely normal behavior. As long as she's not doing too much damage to the point of serious damage to the male, I wouldn't worry.

As for the fin rot, did you qt any of the fish? You may end up needing to take all the fish out of the tank and putting everything in a qt tank to treat them.