chances are the brown algae are diatoms, it is normal for them to be there in new tanks. You probably could cut down the lighting to 8 hours a day until you had serious need for it. If your tank contents list is current, you could use a heck of alot more snails. Also, a a side note, the choc chip will eat corals and unless you are seeing your mandarin eat the foods you put in the tank, it is probably not getting enough to eat.