[Reefland]

I think everyone that has experienced RTN (aka RTD or SDR) or has read about it is unclear of the cause, including the full-time researchers in our hobby. Just getting over a recent, first case of RTN, I wanted to post a thread and get some thoughts on the condition when you experienced it.

In Borneman and Lowrie's research, it is mentioned that "no consistent or obvious bacterial population" was found is more than 400 separate cases studied. However it is also mentioned (and I think this is what we experienced) that introduction of new corals can affect other healthy corals in the system while the new addition remains unaffected. With this in mind, it seems logical to me that some type of bacteria or pathogen has to be introduced with the new coral addition, and transported to other corals in the system for the condition to begin.

It is also thought the condition be realted directly to stress of a coral. Drop in ORP levels is specifically mentioned and I know that recently Chuck (please jump in here) had experienced some RTN on some colonies after doing some maintanence in his refugium, causing some sediment stirring; thus the possible drop in redox levels. Other stress causing conditions would be temperature related or other various elavated water conditions.

With this said, what were some of the event's that occurred when you experienced any degree of RTN in your system? Has anyone ever experienced the condition without any of the mentioned additions or changes?

Thanks,

[SueT]

This ought to be a very good thread Scott. IME, when I had an outbreak of RTN it was inconjuction with either adding a new {wild} colony or the stirring of the sediment {mud} in my ecosystem sump. In the past 6-9 months I have stopped adding any wild colonies and have gone to almost 100% captive raised frags and I have not had any RTN events at all. That is not to say it might not happen but I have found these corals to be so much better at fighting off any kind of condition like RTN, SDR or just failure to thrive. I think when something like RTN happens it can be traced back to some varying degree of difference in routine maintenance or difference in additives, or an unhealthy coral added to an already healthy system. I do believe wild corals can bring in Heavens knows what and wreck havoc in captive systems. That is kind of what I was asking about dipping corals in montepora's thread.

How much does dipping help in this respect?? 50%...75% or is there any idea?? In the 1 time I have had an RTN event it also only involved a couple of wild colonies. It never happened and went all over the system but only stayed within a small area. This was in my 180 so there was a bit of room it could of spread to. I could not even tell you what stopped it other than my immediate notice of it and immediate response to it. We all have read the threads about some loosing their entire coral population and the others that may only loose 1 coral to it.

I also think that after experiencing such an event as RTN or something like, the system needs to be left alone and let it recover before adding anything new. I believe this so stresses out not only the corals but the entire system.

There is a wonderful article I have printed out that Eric Borneman and Jonathan Lowrie wrote about "The Immune Response of Corals". This is Part 2: Models for RTN".

my 180 ecosystem sps/clam tank:
http://berlinmethod.com/suet/
my 120 ecosystem sps tank:
http://suetruett.homestead.com/home.html

[Reefland]

Hi Sue!

The event we just recently encountered was "mild" compared to the stories I have read and heard about; only afffecting one wild colony and 2 frags. After doing some additional reading on RTN I was suprised that it attacked 2 M. digita frags that had been in the tank for a couple of months; Borneman states it is "Uncommon" for M. digita to be affected. Of course nothing is written in stone regarding RTN being the mystery it is. Of the 3 coral that were affected, none of them lost all of their tissue. The event last about 2 days and as of now, all 3 of the corals are still in the tank and what tissue remain is showing polyp extension and good coloration. I think I will just frag what I can of the wild colony but I am going to see if the M. digita will recover.

If I recall, montepora had a recent addition to his tank when he experienced the RTN recently. Again, logic tells me that if this is occuring after a new addition, some type of bacteria or pathogen is being introduced. Perhaps the study I referenced above didn't find anything consistent because there are multiple bacteria that induce the condition?

Is the article you mention online? If you wouldn't mind, I would enjoy reading anything on RTN that you have so if you know of some online articles, links would be cool!

Regards,

[zhenya]

http://reefcentral.com/forums/showth...5&pagenumber=2

Hi Scott, have you read through this thread yet? I too read as much as I can about RTN,having witness a couple in my tank.So far I was able to salvage one frag of an Acropora species that was affected. Like in your case the tissue loss was not as rapid? as in cases I've read about,but nonetheless the entire colonies were consumed intime(2-4 days usualy).
What this guys are discussing in this thread is fascinating to me and I hope you find this interesting read,unless you already done so.

[SueT]

Scott, this article was online at FFE some time back. Yes, montepora spoke about introducing that seriatopora colony from his LFS I believe. I would never worry about anything from my LFS but I imagine some are quite different. I have spoke with some that have had RTN events take a otherwise healthy acropora spp. colony and it be gone in as little as 30 minutes. RTN is rapid and I think a true RTN wouldn't last for several days. Then with this condition being known about as much as when I got back into this hobby it seems like not much more is known about it.

Montipora digitata is a strange one to bleach for sure. Then again who knows. All I do know is if whoever figures out what causes it and finds a cure for it will certainly be a millionaire several times over.

my 180 ecosystem sps/clam tank:
http://berlinmethod.com/suet/
my 120 ecosystem sps tank:
http://suetruett.homestead.com/home.html

[mrok12]

Sue,

DO you think that cultured corals from wild colonies that are sent when they are small adapt well and can ce considered better than wild full colonies at fighting off stress and infection?

MROK

[MtnDewMan]

Ohhhhhhh, a topic I would love to know the real answer to. I definately have been experiencing some RTN events of late. In the past 3 weeks (just prior, yes, I did some maintenance in the refugium that I believe stirred up and/or had some die off consequences that made it's way to the main tank). I have currently lost 4 small colonies in the last few weeks with others showing some sign of stress. So many factors can really get to the coral. Spikes in ammonia, nitrites, nitrates, redox reductions, sand storms, flow changes, temperature changes, chemical fluctuations, etc ... I am sure the list goes on and on ...

I have read the pros and cons of UV sterilization. That is my next project, to give that a try to help clean up the water. There are lots of good things in the water column for our inhabitants, but there are also lots of nasty things in our water column as well. After this latest experience, I think I will try to get rid of the nasties as well as the water column goodies to see how that does for the tank.

Don't get me wrong, my tank isn't falling apart yet, but it certainly scares me

[zhenya]

Interesting observation,Chuck. I had a table colony go RTN and after some fraging attempts I moved it up in the tank for some heavyer current. The colony died anyway but now the frag of A. millepora that I got from Patrick Monaghan is showing some tissue loss. it was doing great and growing like mad untill I moved that other colony close to this frag. Now I'm facing another loss I think.Well,judge for yourself....

[SueT]

Chuck, I have heard good things about using the uv sterilizers to remove or hopefully remove some of the bad pathogens. Whether the pathogen that is RTN will be part of that is the million dollar question. I also think your system has a long way to go before falling apart. I think a true RTN event is not careful of what gets it and what doesn't. All the mentioned are so intricate in whether the entire tank becomes affected or not too.

Mike, I think anything that is not a wild colony has a better chance of doing well than any grown wild coral. I think the whole deal though is the further removed from being a wild coral the better off the chances are for survival. This again is JMO, I think wild corals are so acclimated to the wild that any collection has got to the a stressful thing. I have seen what some of these wild corals look like where they have been blasted off rocks in the ocean and it is hard to believe that it was't hard on the coral. Then all the transportation and then to our LFS and then to captive systems it all has to come into play. Any little thing and it sets the coral off on stressing and being stressed can only bring about the end.

my 180 ecosystem sps/clam tank:
http://berlinmethod.com/suet/
my 120 ecosystem sps tank:
http://suetruett.homestead.com/home.html

[zhenya]

Hi Sue ,

How are you? FWIW, the colonies that RTN in my care were not wild,they were W.Smith colonies from Allen Mabee.But nonetheless,I don't think UV will help as I run it on my 75g tank for a month prior to the event. I have no clue as to why this happened in my tank.Your frags,Sue,are not affected at all and other colonies are doing great as well.But this thing scares the living crap outta me I'm not prepared to fight it at all.All the lugol's dips I did and fraging,did not help me at all.

[MtnDewMan]

Gene, it does appear you are losing something there, hard to tell in that picture though unfortunately .... Good luck with it, keep an eye on it.

Thanks Sue for the encouragement. You are definately right, the UV sterilizer probably is a long shot, but hey, we have lots invested in these boxes of water, what's another piece of equipment to further the overall quality of the water

edit: For what it's worth, I have had near zero success fragging an RTN'd colony and getting them to survive.

[zhenya]

Chuck, thanks! I could not believe how fast that frag encrusted and started to grow and now I'm not sure if it'll make it or not. I'm thinking of maybe puting a bandaid like suprglue fix for now and hope that it will grow over it. It is a good size tissue loss,about 3/4" on a small frag that started from 1 1/2" piece. I'm expecting a frag from Steve Tyree(Echinopora) in March and now this RTN thing

[SueT]

At one of our MARSH meeting awhile back Eric Borneman or it may have been James Wiseman showed a slide show of Walt Smith's facility. He grows these sps out in lagoons. I would consider them wild as the native people only fix them onto those plugs and then replace them right back in the ocean.

Chuck, I know what you mean. If money can buy it then I'm for whatever can help with our systems.

Gene, I might email Steve and see if he can put your echinopora off for a month just to see what happens in your system. I have tried echinopora 2 times and it is a hard piece to grow in the best of conditions. I got one frag from Steve and another one from someone else and neither grew any. They are very funny about lighting--low, current--next to none and then you have to cross fingers and anything else to see any appreciable growth.

my 180 ecosystem sps/clam tank:
http://berlinmethod.com/suet/
my 120 ecosystem sps tank:
http://suetruett.homestead.com/home.html

[MtnDewMan]

Something I just remembered ....

Prior to mucking around with my refugium and I believe one of the reasons I was mucking with it so much is that it had a ton of flatworms in it. None at all in the main tank, but lots in the refugium. My thoughts are now that after messing it around, did I kill a bunch of flatworms and the toxins released into the system? Hmmm, I don't see the flatworms in my refugium anymore, although I tried to pull them out by hand with caulerpa ... Caulerpa disturbance could also be a factor I guess ... so many things that it could have been that started the chain reaction huh?

[zhenya]

Thanks for your advice Sue. It is sertainly something to consider for me but I'm actually trying to set up another tank as we speak,just for the frags that I'm planning on geting from people. I will let this thing run it's course and see what happens in my 75g and wont put anything new in there for a few month. I'm also runing GAC and doing water changes in hopes of diluting whatever is there.

[zhenya]

Chuck,

In that link that I've pasted,Eric talks about survival rates for SDR/RTN and I believe he said that if you place it in a different/separate tank,the survival rates are good. Another que to set up a quarantine tank ASAP for me I think. I just wish I had a room for all this

[SueT]

Chuck, I think that is a very good idea you have. Flatworms do excrete a toxin when they die and I'll bet this did play a role in the scheme of things. Hopefully with your doing what you are it will not be any more dramatic than what you have seen. I had a few flatworms in my 180 and I never knew where they came from but a yellow coris wrasse did them in.

my 180 ecosystem sps/clam tank:
http://berlinmethod.com/suet/
my 120 ecosystem sps tank:
http://suetruett.homestead.com/home.html

[MtnDewMan]

I am hoping things are slowing down from the RTN perspective at least ... Here is my latest loss ... all of a sudden, poof ...

[Reefland]

Yeah I am thinking it is slowing down on our end too; at least we hope. We added a couple of nice frags this weeks from www.ocean-oasis.com but do not plan on adding anything else for a while to make sure everything is stable. Luckily I still have some frags that I plan to trade out during our swap in April.

Regards,

[Reefland]

We have now experienced two different events and two different causes. The second was most likely due to stirring up the sand bed when I removed all of our LR to scrub it free of macro algae. The macro algae growth was most likely due to a high TDS from our RO/DI water. During this event, we lost corals which I know where wild colonies, or frags from wild colonies. All of the corals that I beleive are cultured frags made it through which is small proof that cultured corals are more hardy in captivity.