Montiporas bleaching

[chase613]

My montipora red caps are bleaching and I don't know exactly what's causing them to do this. I have kept them in the same position in the tank for about a year now with great coloration. But now all the sudden the colors started fading and they started to bleach in the middle of the colonies. I'm just trying to figure out what's wrong so I can fix the problem fast with little harm to the corals.

Parameters
Salinity 1.024
Alk 9.4 dkh
Calcium 440ppm
Magnesium 1275ppm
Phosphate .06
Nitrate 10ppm
Temp 79.5-80.3

 

[dinger28]

When my Alk was 8 or below my red month was doing amazing. When I went to above that I noticed the color started to fade and then it bleached out over a period of a few weeks.