Shedding 4'' Blue Acro

[jer77]

I bought a really nice blue Acro recently. I am not to experienced with keeping sps but am really trying to. I have many manti caps and digis and two other acros that when I got them they experienced similar problems. They would slowly bleach from the bottom up. The first was an acropora valida. It recovered nicely, but still hasn't grown down to its base its just growing upwards, but its colors came back and its purple with light green polyps. The 4'' tall purple/blue acro I recently got has begun to not bleach, but its tissue has begun to recede and flake off at a fast rate. I'm worried by tomorrow all of it will be white. Could this be caused by high levels of Ca and Alk? I was adding lots of CaCl because I grow halimeda in the fuge, but recently most of it got overgrown with hair algae so I trimmed a lot of it. What resulted was a high level of Ca. Right now the Ca is 500-520, and the Alk is around 9-11dkH. I have done two 15% water changes and the Ca still hasn't gone down more than 10ppm. Do you think if I just do more water changes and keep the Alk high to balance the high Ca my shedding problems will stop on further acros? Do you think the shedding only happened with the new coral because it was shocked and the other corals gradually got used to it? My phosphate kit sucks but the nitrates are zero. I don't believe the phosphates are higher than regular. Thanks for anyone who read all my rambling!

 

[echopiece]

Sounds like RTN (rapid tissue necrosis) to me. No real definite answers why SPS do this but it could have been from stress or improper acclimation. I've had that happen to several new SPS frags in the past. You could try and cut a piece of the frag that wasn't shedding to see if you could save it. But the odds are against you.

What salt are you using? If you use a salt brand high in Ca and Alk, it won't come down with water changes. Those numbers don't seem too bad though. So many things play a factor in these delicate SPS corals. Did you acclimate the coral properly, placing it low in the tank so that it wasn't shocked by your lights?