Ideas Please

[Crazy fishes]

Hi ladies and gents,
 
I have a little problem in my hammer coral keeps committing suicide; the tissue of the coral is peeling away from the skeleton. My tank is 6 years old and running very well with no problems up to now. This coral has been in there since the beginning and thrived with several fragging sessions in this time period. I do a 10% water change weekly without fail and have just tested parameters which are all fine. The exception is calcium and magnesium are borderline low. 
 
Temp 24C
SG 1.025
Ph 8
Kh 8.15 dKh
Ammonia 0
Nitrite 0
Nitrate 0
Phosphate 0 
Calcium 385
Magnesium 1285
 
I do have a lot of macro algae covering the rock work but I have a perfectly healthy maxima clam in the tank which is fine. The only things I can think of is 1) the recent introduction of Zoa 2) macro algae is irritating 3) old tank syndrome
 
Anyone have any additional ideas to help safe my hammer coral. 

 

[CezzaXV]

What lights are you running? If it's not LEDs, perhaps the bulbs need changing?

 

[Donya]

Sounds like it may be the start of polyp bailout, which is potentially hard to figure out. From what I've read on it, a lot of people think it's environmental and then blame all sorts of things from lighting to phosphates to magnesium. That's what I've read though, not what I've seen. I've lost several LPS to polyp bailout over the years and every instance has had its root in some sort of obvious physical/chemical irritation:
-incompatibility with another coral in the tank or proximity (move the offender and it stops)
-encrusting animals digging between the coral and skeleton (there are some rotten tiny snails that will force in and dig about)
-infection setting in at the site of physical damage near the skeleton
-being stung by something like a potent anemone or some other animal with strong irritants/toxins (anemone stings, sweepers, etc...recently had a hammer bail to a Diadema setosum sting too)
 
That said, I do not consider myself a coral expert so I may have just seen some really weird cases. It's obviously worth getting the params to ideal levels as a first step, and perhaps doing a couple of larger water changes in case it's some other weird thing you haven't tested for. The fact that the clam is fine suggests that the lights are ok, although if old bulbs are still worth changing just in case on non-LED as Cezza mentioned. 

 

[Crazy fishes]

Led lighting (Reefbeam 120) in use for the last 2 years. I thought it was possibly the Zoa as it was fine up to their introduction. They produce platy toxin which are pretty noxious. It is a shame because they are high class Zoa; really fluorescent under blue lighting. Looks like they will have to go or otherwise no LPS. I have noticed that the bottom polyps bailed first which could be explained by irritation from the thick layer of macro algae on the rock work. 
 
Kindest regards