Acropora’s are Brown

[james.96]

Hello all, I am finally starting to have success with some SPS corals such as Montiporas, but not having success with others. I have one montipora that is bright red (not pictured) and the other that is bright green with red polyps (pictured). Although their coloration looks good I do not have great growth. I also have a stylophora that has good polyp extension and ok coloration with little growth (pictured).

I also have 2 acroporas in my tank that have turned brown showing little to no vibrant coloration (pictured). There does not appear to be exposed skeleton at all. And there is little to no growth and little to no polyp extension.

Lastly I also have one other unknown SPS coral which has a browning color and little to no growth and polyp extension (pictured).

My current parameters are:
Salinity: 1.026
Nitrate: 12
Phosphate: 0.0
Alkalinity: 9
Calcium: 500
Magnesium: 1400-1450
Average pH: 7.97

Current lighting is Radion XR15 G6 pro using the preset AB+ spectrum at 75%.
My tank is 60 gallons measuring 24”x24”x24”
I use tropic Marin pro reef salt and dose the tank daily with bulk reef supply 2 part. I also use brightwell coralamino 1ml daily.

Any recommendations are very much appreciated. Thank you. Feel free to ask if there are any other questions you have.

 

[Lavey29]

I have a similar size tank and run my XR15 lights at 100% intensity on AB plus with good acro growth and color. Browning is typically lights or excess nutrients. You need some phosphate.