help with hydnophora!!!

[subzero]

The large one is the one that's effected.. i noticed a couple of days ago that the tips started getting brown.. on closer look it was algae. Then, on even closer look, it seems that the green tissue has withdrawn and in that area its just the white skeleton...

what's causing this? the other smaller hydnophora frags (from same colony) are doing fine. how can i stop it?

 

[Suohhen]

How long have you had this piece? One thing that can happen is called burnt tips typically associated with high alkalinity especially when paired with swings which could be caused by dosing that isn't preformed frequently enough and dosed in unsafe amounts or a newly added coral that went from a low alk to a high alk.
Basically what your seeing regardless is dead tissue that becomes a food source for algae. If it stays isolated it isn't typically an issue but if it is progressive tissue loss the typical result is a total loss of the coral given enough time, the most consistent mitigation is to frag off the healthy tissue. That doesn't seem to be what is happening here but it is impossible to say for sure.
One other big possibility is that it is getting blasted with too much light. If this is a new coral did you light acclimate?

 

[subzero]

thanks... i'm going to do a bigger water change and see what's going on. no light acclimation problems it was doing fine until i did a 5 gal water change with water purchased at a LFS... seems like maybe that water was bad for some reason but nothing else is being effected..

 

[Suohhen]

Sps is very sensitive to changes, especially sudden ones. Salt mixes often have abnormal amounts of elements that are very important to sps such as Alkalinity and Calcium. IO is typically low and Reef Crystals is pretty high. The safest thing to do is test the alk of both your tank and the make up water and make sure things aren't too far apart. Typically many small changes are better for Sps. Also how have you been maintaining your parameters?