<a href=showthread.php?s=&postid=14831749#post14831749 target=_blank>Originally posted</a> by kenargo Having just experienced my 1st bout or RNT I noticed that it appeared to begin at the base and move up. My wife asked; does it always do this or can it also start at the tips and work down.
RTN is simply just a broad statement (usually to describe a sudden/rapid coral death or decline) and not actually a disease. Rapid Tissue Necrosis is a statement "made up" but the hobby and means absolutely nothing outside this hobby.
There are many, many coral diseases (many are not well understood) but RTN is NOT one of them
So to answer, it can be whatever you want it to be and start wherever you want it to start.
Yea, I am sure that AEFW is not what I had. Whatever happened stopped after 4-5 days and there was nothing visible on the corals and remaining corals are fine. The corals that did not 'shed' tissue are well, in fact some larger colonies had part of the coral white and others remained well. This happened very rapidly (e.g., within 12 hours, 8x4" coral gone and affected 80% of the corals in the tank to some degree). I don't know what caused it; nothing measurable in the water that I was able to find, but in defense of the problem I increased carbon, skimmed wetter, water change, etc. It stopped as quickly as it started, some corals gone completely, others died at the base to within a short distance to the tip (e.g., 1 coral lost 4" of tissue from the base but the 1" at the tips remained).
Back to the question at hand; it appears that the answer is no, there is not any set statement that says coral tissue recession starts at the base and always moves up; like I said it was just a question I was curious about.
Thanks Gary, I think I'm OK with flow PE tends to run fairly well extended and I'm running 4 Tunze 6205 + 2 6055 on a controller which I can see a constant rocking back/forth of the polyps. My suspicion is that something airborne got introduced into the tank but it's just a guess. Since it's no longer happening I am less stressed now but I'd like to figure it out. I can tell you I was on pins and needles for the few days this was happening!
No, the corals in question had been purchased over a year ago as little 1' frags and had grown to rather large colonies since then. Nothing recently added, no changes in routine, nothing I could point to.
jeez- small frags grown into large colonies with no change in routine would normally have me question water flow (again) but all of the Tunze's should have been providing plenty of movement.
The airborne theory is a plausible one. I've seen a lot of crazy sounding airborne things affect Acros- hairsprays, candles and even grease from frying Italian sausages!
Since it happened so quickly and then stopped, that's a head scratcher. I know you would have caught any abnormal swings in temp or pH on your AquaController, so a temperature spike or a kalk overdose is fair to rule out. Anyway, glad you got it fixed, Ken.
When I've had problems with STN from the base up, it's always been because of phosphates. It isn't quick, though. The tissue slowly dies over days and weeks, rather than hours. As soon as I put a fresh batch of GFO in, the necrosis stops.
I think you are probably right that it's some sort of contaminant, which the carbon took care of.