What's up with my Acan?

I'm going to get test results in a minute, but here's a picture in the mean time. It was fine as recently as 3 days ago, fully open. Now, there's this stuff on it, and it seems like it's on another acan too. On the other acan, the tissue doesn't look nearly this bad (it still has color, and is fairly tight against the skeleton, but this one looks to be pretty well dead at this point), and this stuff is just in between the polyps.

 

Looks like RTN to me.

 

Jeez, what luck. RTN on a couple acans, in just 3 days...

 

I think it is gone since your limpit is on the skeleton. +1 RTN

 

+2 toss it before is can spread. Frag the other acan colony.

 

How close and what kind of acan is the other one? I have several different types of acans and one, its called Fruit Salad Acan Echiada I think, has really LONG sweeper tentacles.

It has killed several of my other Acans and that is exactly what they look like after being attacked. It took a few attacks for me to figure out what was going on, I only figured it out after I actually saw it doing it one night.

And to be honest with you, I thought that RTN or Rapid Tissue Necrosis was limited to SPS, I might be wrong though.

 

They're halfway across the tank from each other. One is up in the top left, the other two that are affected are bottom-middle. That would be about 18" apart from the top left one.

Test results:


pH 8.4
Amm 0, Nitrite 0.1 (test kit always reads 0.1, I think it's faulty) , Nitrate 0 (have an algae issue ATM, so it's not surprising)
Phos < 0.05 (just got the reactor back up and running today, has been off for a week, along with carbon)
Cal >400 <450 (increment of 50 on the kit)
Alk - 1.6 meq/L (low, but I don't think it's horribly off since pH is good)
Mag - 1700 (fightin bryopsis, that algae outbreak mentioned before, so I raised mag with topoff over the past week)

Could bryopsis be the cause of the acans going downhill? I heard bryo does chemical warfare; could that, in an outbreak, with no carbon running, with bryopsis growing right next to my second-largest chalice, have hurt them so they became susceptible? My torch is doing pretty well, and the frogspawn seems to be normal. I thought those guys were more sensitive to chemicals, so I didn't consider it.

 

Get your alk to 2.5 don't use pH as an indicator of good alk. They may have reacted to the addition of mag.

 

Ugh, I just got home today, and 2 more acans were completely RTN'd. I tossed the other ones about an hour after the first suggestion. Every other coral in the tank is fine; it's just the acans that are going down. The survivors aren't open like they used to be.

Is there anything that could be in the water that's doing this??

 

Kinda looks like a brown jelly issue to me...