I have a 75 Gallon reef tank. It has a 20 gallon sump tank, and has been set up for about a year. My sand forms a brown crusty algae on it though. I was wondering if there was something wrong in my power head placement. I have attached a picture of my tank. There are 3 Maxi Jet 1200's and one Maxi Jet 900. There is also the mag 4 pump which returns from the sump.