RTN or bleached? Pictures attached

[MarcWeaver]

Is this RTN or bleaching? It happened overnight last night. There were no parameter swings - alk is 8.5, calcium 440,mag 1400, pH 8.0-8.2, phosphates .03, nitrates 9, temp 78-80, salinity 1.025. The blue stuff in the "now" picture is the flesh of the coral sloughing off but the polyps appear to be there. I thought RTN takes out the polyps as well. I am moving it to the bottom of the tank to see what happens.

A few days ago:

Now:

 

[OneReef]

Looks like recession to me. If bleached, there would still be polyps where the white is

 

[MarcWeaver]

Thanks. I thought so. Are the light blue things in the picture the polyps or are they some kind of chamber or tube where the polyps once were? Here is a blown-up picture

 

[karsseboom]

Looks like it might be bleached or something is bothering it.

 

[MarcWeaver]

I moved it down. All other SPS are doing fine. It must just be one of those things..... It definitely has polyps though, I could see them moving when I moved it.

 

[ange062]

Definitely not RTN, it would be ghost white if so. Probably just bleached or acclimating to the new tank (looks like a new frag). Give it a little time and it should be fine.

 

[MarcWeaver]

Just to follow up to complete this thread - is was RTN after all. Today the frag is bright white with no polyps at all. The polyps must have been the last thing to go. This was a fairly new frag at 3 weeks and was starting to color up nicely from the LFS's phosphate-ridden water. Bummer. Maybe it was shocked from the over 1ppm phosphate water to my .02 phosphate water. Other frags purchased at the same time from the same place are doing fine, though.

 

[OneReef]

Yes, there were polyps in the picture, but I was referring the the base which looked bare white.

 

[MarcWeaver]

OK I understand what you said now. Thanks. I figured out the problem I think - chronically low alk. I measure alk with a hanna alk checker and what Boomer said is true about the 10% to 18% high-measurement factor. I just read the extensive post the night this happened and took my water to be tested on my friend's salifert and it was 6.8 and has been lower than that with the correction factor applied. Even my star polyps were closed. I dosed enough soda ash to raise it 1 dkh a day for 2 days. Now alk is 9 and star polyps are back open and SPS look much better today.