plant/green algae control.

Question
To give you a little background on my tank:  
I have a 75 gallon saltwater tank.  There is about 150-200 lbs of live rock, a manderin goby, lawnmower blenny, purple lobster, cleaner shrimp, and a few corrals (polyps, brain, hammer,torch, mushrooms, and the pulsating fingers).  The lighting use us to be a florecent bulbs with the moonlights and a small led light, but now there is a metal halide system that was just put on a week ago.  I believe i have told you all that you should need to know.  So would you be able to tell me why I have so much green algae or plants growing on my live rock??  In the year that we have had the tank we have taken the rocks out 3 times trying to clean off as much as we can.  Also from time to time we try and take off as much as we can, but it just seems to grow back so fast!!  Please advise!  

Answer
Hi Patti,

Sounds like a very nice setup. I would begin by checking your nitrate level. Algae thrives in a nitrate rich environment. Also I have found by raising my lights about 6 to 8 inches off the surface of the tank helps to cut down on green and brown and promote coraline algae. Gerry.