20 gallon reef tank help

[nport19]

i currently have a 20 gallon reef tank that's been running for about 10 months now. One of the problems I seem to be have is brown alge is taking over my sand. The hermit crabs and snails don't seem to be helping with the problem. Any ideas on how to get it to go away? Also any advise on how to get a sunrise dotty back to stop be aggressive towards my clown fish?

 

[Russellaqua]

What are your water parameters like? Phosphates, nitrates, ammonia, nitrites etc? Those can help us figure out what's happening here.

 

[nport19]

All my levels are were the should be. At least that's what I was told by the guys at petco. If this helps at all the tank does sit in front of two windows that get a lot of sun coming through them and then to the tank. Also my salinity is .26