ok i have been getting this brown algae all over my rocks and sand yes i know it diatom i dont know why im getting it now the tank been running for the past 3 years the only thing i did new is the LED'S lights but they have been on the tank for about 4 month i got a little brown algae at that time but it went away i test the water everything was good and i test the RO unit and that was good the funny thing is im still getting green algae on my glass thats why i dont get it

