I am gonna have to disagree on the bioballs, the bioballs are not going to remove your waste they are just going to trap and concentrate it. I would get LR rubble in there that will act as natural filtration. you may want to cut down on feeding a bit also. and the UV bulb would help. and yes check your phosphates and maybe get some phosban or something similar. I would also get some snails in there and get a cleaner crew.
how long have you had the tank up and running and how long are you running your lights?
and how often are you doing waterchanges and how much water. you might want to consider doing like a 25 gallon water change too that would help bring the levels down.