Coralline Algae turning brown?

[quaffin1]

Our coralline algae has been developing over the last 6 months in our new
75G reef tank. Noticed this week that the purple coralline algae on one side of the tank appears to be turning a dark brown.
Sometimes when testing the Calcium levels it drops in the 380 range,
otherwise it usually tests 400-440.
Nitrates generally staying at 20ppm, Amm and Nitrites -0
pH-8.0-8.2
SG 1.022-1.023
Temp- 77-80F
Have we let the Calcium go too low and this is causing die off of the
coralline??

 

[essop3]

Usually if coralline dies it turns white. Feel it and see if it's a little soft. Try to scrape off a little with your finger nail. If you can peel it off it may be brown wafer algae. That's kinda what it sounds like.

 

[quaffin1]

Thanks essop;
yep, I scraped at it and it has a soft slimy feel, it will scrape off.
So your probably correct. It is only appearing on the LR on one side
of the tank.
I have been having a little trouble with the MH light sometimes
not firing on that side. My tank setup is approaching 6 months.
But the LFS set this tank up for me and I noticed that both bulbs are
not the same manufacturer, leading me to believe that it is possible that
one or both bulbs could even be used when my tank was put up.
This could mean that the right side bulb is older and loosing some
spectrum.

 

[essop3]

If it is brown wafer algae the only way I can find to get rid of it is manual removal. No amount of water changes, new bulbs, or any regular methods have worked for me. I asked the pro's on another site (anthony calfo I think) and they told me the same.
If you only have a small amount remove what rocks it is on and let them dry out. Scrape the glass of what you can while syphoning to prevent spreading small little pieces of it. Try to take care of it before it spreads. I didn't and now have to fight it all the time.
Bob Fenner says Naso tangs may eat it. It is part of their natural diet. I don't know if I'm convinced enough to add one.