Monti cap randomly showing white patches

[eastlake]

So I have a TON of monti caps at home and all are growing well and quickly. There's one very large section though, near the bottom of the tank, that over the last two weeks has shown huge areas of skeleton. It looks like something may have been eating it because the patch from last week had almost totally healed up and then during the course of lights out last night another very large area of white had appeared, almost 3"x3" or bigger. If this was happening to the other moniporas in the tank I'd say the culprit was something with the water quality but right now its just isolated to the one plate. There is an allens damsel that has made a home for itself underneath the coral so I thought that maybe its just doing what damsels do in the wild and clearing coral out of a spot so its algae garden can grow but again it happened after lights out so I'm fearing something far more sinister is in play here. I don't think I have montipora eating nudibranchs as I can regularly be seen with my nose smooshed against the glass looking for such things, I know pictures will help and I'll get some up either later today or tomorrow, in the meantime any info would be greatly appreciated. Thank you

 

[eastlake]

here are some pictures, not the best quality, but you get the idea. The black specks are a couple stray pieces of old carbon and my Atlantic blue tang "Omar" felt left out so he had to get involved.

 

[nmotz]

Hard to say without knowing a little more information. Just based on the photos I'd say either alk swings or parasites caused the damage. Remember monti eating nudibranchs often hand on to the underside of the coral so it might be hard to see them since that coral is very near the substrate.

How stable is your tank chemistry? Any significant changes to the tank recently (equipment, husbandry, etc)?

 

[eastlake]

Nope, no radical or even subtle changes. Still doing 10% weekly water changes and the other montis in the tank aren't showing any kind of distress either, the acros also all look good, which wouldn't they also be showing "burnt tips" if the alkalinity was out of whack? I'll double check everything chemistry wise tonight because all was fine on the last checkout this past Monday. I think I'm also going to stake the tank out tonight to see if there's anything attacking it as it seems that's when the damage is being done. I'll post test results as well as the results of the nights vigil tomorrow.

 

[NaturalReef]

I had that happen and it was due to not enough flow causing detritus to settle on the coral.

 

[nmotz]

I had that happen and it was due to not enough flow causing detritus to settle on the coral.

Yeah I've had this happen too, and it is a possibility since the coral is placed near the substrate.

To the OP, you're right about the burnt tips. That's a dead giveaway for alk problems. Check underneath the plates as well as you can tonight with your flashlight. That's where monti eating nudibranchs hide most often.

 

[eastlake]

I have had some dead spots occur when my damsels are so kind as to dump a backhoe's load of substrate onto the coral and I don't blow it off in a timely fashion. Well, last nights vigil was a bust, no harmful critters that I could see anywhere. Looked as closely as I could under the parts of the coral I could, even looked through the "window" underneath the tank where the damsel cleared away enough sand to allow undertank viewing, doesn't mean I didn't miss them though or maybe the lights hadn't been out long enough, 3 hrs. Also double checked parameters,
KH in dKH= 6.7
Ca= 415
Mg= 1,200
NH4= <.25
pH= 8.2
PO4= .03
NO3= between 0&2
Specific gravity= 1.026
temp.= 78*F
I realize Mg, Ca, and Alk are a touch low so I've come to the realization that its time for a doser, I still think a pest or current inhabitant is to blame for the damage as the rest of the corals are showing no signs of stress or damage. I'll keep posting in regards to my stakeouts for those who are interested.

 

[nmotz]

Calcium is good but your alk is indeed low. That might be your problem in fact. I'd slowly dose it up to between 7-8dkh and keep it there for a while. Your nitrate and phosphate are fairly low, so I wouldn't take it Alk up any higher than about 8.5dkh. Mg could be a touch higher, but I think your low alk is the problem. Surprised that's not bothering your other corals though....

 

[Acromaniac]

Alk and Ca are fine. Try testing potassium

 

[eastlake]

Potassium huh? never heard of testing for that but its worth a shot. nmotz, I certainly agree that I need to bring those parameters up, I'm just baffled that only one cap is showing damage when none of the others are and that the acros, which I assume are way more sensitive to alk changes than caps, remain unaffected. To boot I have an Acropora valida (tricolor) that I lovingly fragged with the back side of my hand while algae scrubbing and the "wounds" have not only healed but put on an 1/8 of an inch in three weeks time. Are monti caps a canary in a coal mine? I always thought that they were the last to show signs of distress. Oh, and last nights vigil was yet another bust. Pods, pods, pods, and more pods. A few limpits, couple of silly bristle worms, snails, and the rest of the clean up crew.