Phos parameter went a little hinky around xmas but are back in check now. I got to it very fast. Have been building up my Mg level as it was almost 0.

My purple tang was nipping at an open brain for a month or more before I separated the two. I think I only ever saw him do it once because he vary rarely would. If you cant move the brain to another tank you can build an egg crate cage to put around it. If it starts to expand again you'll know if something was picking on it.

If you're magnesium was nearly 0 thats a pretty big problem too... can we have a list with all of the parameters you can test for?

How much are you adjusting the Mg per day? But also check your fish or in extreme cases you should even see little bite marks (if you do then you know it's a livestock issue). Also wouldn't hurt to put it in a shadier spot just to see if it responds.

FWIW of the 3 options I'm thinking light is possibly the most likely, so I'd start with moving it to under an overhand or a tank edge and see where it goes from there.

Good luck!

Salinaty 1.026
Calcium 440
Mg 1250
Amonnia 0
Nitrate 0
Nitrite 0
PH 8.4
Phos .5
KH 11 dKH

Was doesing the max for the first 5 days, then switched to Reef Cystals and did a small water change of 10% and now it is @ 1250. A little low yet but I am planning on a 20% water change this weekend.

Can't see any nip marks on the brain. Moved it to a diffeent spot closer to the rock but don't really have any shady spot's.

Well I moved both of my brains to a different spot as shaded as posible. My one brain has responded and opened up more then it ever has but not the one I had posted the pic of. Hope it respond's.