Coraline on glass but not on rock
 

I have a descent coraline algae growth on the glass, but almost none on the rocks, and during the past several weeks there is macro algae (brown, bush like) growing out of the rocks. Could this be an indication that the nutrient level is high.

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it's a 29g boceanic bio-cube with top removed (suspended MH), skimerless, but with 15% weekly water change. fishes are one small perc clown, one small pygmy angel and yellow watchman goby.
forgspawn, tocrh and xenia colonies are doing fine. Green candy cane has not expanded in a while

Water parameters are:

- Nitrates: approx. 12 ppm
- Salinitiy: 1.026
- PH: 8.3
- Calc.: 420 ppm
- Alk : 9 dkh (salifert kit, not sure if the kit could be one of the defective ones)

Lights are 175MH 10000k that are about 13 months old. Not sure if this is a factor, but any way I am expecting an Iwasaki 175w 15000k in few days.

Any opinions on the lack of coraline on the rocks, as well as the unsightly macro algae growth

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.

algae
 

-coralline algae seems to be spreading like wild fire in my tank, red especially,
as long as my calcium levels are in the low 400's-

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

With that much rock and sand, I'm surprised you have any NO3. What do you feed? Frozen foods can add a lot of nutrients. Is the sand bed old(over 3 years)? How about the rock? Is it clean on the surface? Try using a turkey baster to clean it off and open the pores, the internal (anaerobic) surfaces are where the NO3 is broken down, make sure the water can get in there.

I basically feed formula one flakes. The sand bed (which is about 3/4") and the live rocks are nearly a year old. I set up the system last September. I am suspecting the additives I am using. Currently I am dosing Salifert's All in One and Coral Calcium. When I set up the system last year I was using C-Balance only and there was more coraline on the rock and less on the glass. When I ran out of C-balance I decided to try Salifert's additives and it might be they are the culprit. I will switch to C-balance again and see if it makes a difference. I also got my Iwasaki bulb and hope it helps too (BTW the bulb is fantastic)

Well, everything sounds in order. Maybe a couple of bigger water changes to knock the nitrates down.

will do

Using R/O and not tap water --- correct?

how long dose it take to start getting coralline algea on the glass?