White spot on Montipora

[Popcorndog]

My sunset Montipora developed a large whit spot 3 days ago. It is slightly larger but not growing much since the initial date. I have siphoned the spot using airline tubing, no red bugs or nubibranches after the first siphon, but plan to siphon again over the next couple days. Interestingly, there was a small pile of white sand just below the spot where the coral skeleton appears to be disintegrating. The white spot also disintegrated some under the siphon? Is this just some STN or any other ideas with respect to what I am dealing with?

Water parameters
N 0.2
point of sale 0.4
Cal 430
Alk 8.6
Mag 1380

To note, I did have another Montipora RTN on me, fragged it up this week. Again, no bugs came off the frag.

 

[Popcorndog]

Also, I have observed my bicolor blenny nip at the coral, but not often. He nips around the tank elsewhere too, none of the other corals exhibited a patch like this from his nipping, usually only pulling their polyps back for some time. I also have a cleaner shrimp, pistol shrimp, Pom Pom crab, Halloween hermit, and a bla

 

[Popcorndog]

These pictures taken today, you can see the skeleton is eroding away. Slightly bigger than before.

 

[Highgrade]

Your parameters look to be good. Can you confirm if sand or detritus is settling in that spot on the monti? Most likely it should bounce back given there are no pest or anything else such as neighboring corals stinging it.

 

[Popcorndog]

I don’t believe anything is close enough to sting it. This seemed to occur the day after feeding my corals, last Friday. I do spot feed. The sunset is getting a mix of reef roids and frozen Cyclopods. I did leave the pumps off for a longer period this last feeding. Maybe an hour or so. Here are its neighbors.

 

[Highgrade]

I've seen where spot feeding and food settling on the corals will burn the tissue if it sits too long.

 

[Popcorndog]

That is one possibility. I have noticed that Reef Roids can clump some and settle on top op the corals. Blows off as soon as the pumps are back on. Not sure if such burns would cause the disintegration of the skeletal structure. Will keep watching.

 

[Popcorndog]

Discovered the culprit after the lights were off for awhile, siphoned two nudibranches. I do a coral dip using Revive on all my corals, must have been an egg on one of them. Hopefully they didn’t lay more eggs and the couple are all that I will see.