Interesting experience with RTN...

[Delphinus]

I actually think that RTN can also be called by protozoan, fungal, algal and bacterial causes.

It's sort of a double-whammy. Either conditions can be such that it will trigger RTN and STN quite easily, in which case, if one coral gets it, so too could a lot of others.

But also, because of the fact it could be protozoan, bacterial, fungal, algal, etc. -- once one host is "depleted" they look for another host and wham - again the chain reaction (even if conditions aren't "right" for promoting RTN).

Either way, RTN tends to be bad news.

I've been battling RTN and STN in my tank ever since I moved (THREE YEARS AGO). It started about 6 months after I moved. I think that I correct the cause, things are fine for a bit, then I'll have another mass loss event. You don't want to know how much money in frags I have lost in 3 years. It's now at the point where I am really uncertain about continuing in the hobby. Things are in a "holding pattern". I still have an empty 280g ready to be set up, that I've been working on, on and off for a while now, .. but .. when I look at my other tanks and see the list of problems that need to be solved, I get badly demotivated. A 280g with any of the same sorts of problems is going to be a nightmare of uncomparable magnitude. If I proceed, it has to be from ground zero. Problem is, I love my fish, they're pets, so I keep at it for their sake. But corals? Meh - I've been burned so badly on this now I honestly can't say that I care for corals other than being able to look at the pretty colours once in a while when they're not trying to have a massive death event.

Anyhow, ... sorry to rain on your thread. Hopefully your RTN is an isolated issue and not anything like mine.