Need help determining cause for RTN

[hilde123]

A few of my corals have RTN'd lately. One is a Pocillopora of which I have several small colonies and one large. THe one large is RTN'ng but the little ones look fine (see pic below). Also I have a red chalice that is receding quite abit (see pic below). The Pocillopora just started RTN about 2 days ago but the chalice has been receding slowly for the past few weeks. I cannot determine what the cause of this is. I have replaced carbon in the sump on case it is some type of toxin. A little info on my tank; Tank is 180 gallon mixed reef (soft corals, LPS, SPS, and clams) with a 55 gal fuge. Circulation is 2 Iwaki MD-30RLXT return pumps, Iwaki MD-70RLT on OM 4 Way with 4 penductors (runs for 30 mins every 4 hrs) and 4 Koralia 4 12V on controller. I run an Orca 200 skimmer and run ozone (30 mg/hr) into another skimmer (acting as reaction chamber) which is on a controller. I also run GFO in a reactor (trying to combat a hair algae issue --- have almost beat it). I run a calcium reactor and kalk reactor as well. I do have a bad aiptasia/majano issue which just continues to get worse over the years. Can these anenomes be adversely affecting my corals even if not touching (i.e. do they expel any toxins). I am adding a matted filefish tomorrow and hope he will start to eat them up. I only have a few fish (Tang, clown, anthias, and mandrian goby). The tank is about 5 years old. I do 15 gal water changes every 2 weeks and use IO salt. Water parameters are as follows:

Temp - 79.5 - 80.5 (verified by two different calibrated probes)
Salinity - 34.5 ppt
PH 7.8 to 8.05
Nitrate = 0
Phosphate = 0
Alkalinity = 9.9
Calcium = 420 ppm
Magnesium = 1400 ppm
(all tests with salifert test kits that are not expired)


I think I covered all the info that will be needed to diagnose, but let me know if I missed anything. Thanks for the help.

http://i223.photobucket.com/albums/dd317/hilde5962/IMG_4208.jpg

http://i223.photobucket.com/albums/dd317/hilde5962/IMG_4205.jpg

[crvz]

that's not really what I'd classify as RTN, but maybe it's a bit early to make that call. I would primarily suspect the majanos as the culprit. Based on the images showing where they're located, it seems that's what's causing the coral to recede. And poccilipora tends to be incredibly hardy otherwise, I'd be surprised if it's something affecting only that coral and not the other stony corals in the tank.

[hilde123]

The poccilipora is shedding its flesh (coming off in clumps) leaving just the white skelaton. What is the proper term for that, I thought that was RTN? I figured the majano may be the culprit on the chalice but couldnt make sense of the receding at the bottom where it has receded much farther than the majano could reach. Will receding kill the chalice or will it just give the majanos their space and grow other directions? Any idea of what precautionary measures I could take to prevent this issue from become any more widespread?

[zigzag1]

From the looks, I would also lean toward the Majano damage theory. I've had poccilipora forever (came in as a hitchhiker, a few polyps) and I'm pretty sure I couldnt kill mine with a jackhammer. =) It survived all my early, silly mistakes even. Hardy stuff for sure. Looks like you've got a battle on your hands. GL!!