Coraline on glass but not on rock

[argileh]

Originally Posted by reef_raf

Everything but NO3 looks good. How much rock have you got? How much sand? The older bulb and the nitrates will certainly contribute to the algae. You want to get nitrates to 0 and the new light will help. If you have close to 1 pound of rock per gallon, the rock should control the nitrates. If not, there may be too much going into the tank.

There are 31 lbs of live rock, so more than 1 lb/gallon. As for sand there is about 20 lbs of carribsea aragonite. I thought nitrates at 12ppm would be ok. How can I lower it to near zero. I feed sparingly and do 15% pwt weekly, and the fish bioload is low