Recovering from RTN episode.

[MarineDreamer]

On Saturday, February 11th, I added four corals to my tank. Within a day an existing Acropora colony that had been nice and happy since August, started to RTN. The first two pictures below show the colony two days into the episode. The second two show the colony as it stands today. The remaining tissue doesn’t seem to be sloughing off.

So my question is this: Should I fragment the remaining branches, or leave things be in the hopes that new tissue growth will grow over the skeleton? There is a third option, Eric Borneman in his book, “Aquarium Corals: Selection, Husbandry, and Natural History” recommends pulling the entire colony right away due to that the RTN event could spread to other colonies. I want to discount this from happening in my tank due to the apparent health of the corals. I.E. I’ve got full polyp extension, and a good (fast) feeding response, and that affected colony seems to be stopping the RTN event.

What do you guys think?

 

[shallowreef]

I had that hapen to me once. I broke off the white pieces and the colony made a decent recovery. I don't know if that was the right thing to do but it worked for me. Good luck with that!!

 

[jetaero]

HMM, calcium and alkalinity flux is usually what I determine to factor in for RTN. Possibly the new corals sucked it up quickly. it try to not add too much at one time.

HTH

-Josh-

 

[NaH2O]

HMM, calcium and alkalinity flux is usually what I determine to factor in for RTN. Possibly the new corals sucked it up quickly. it try to not add too much at one time.

HTH

-Josh-

I personally think there is more to it than just calcium and alkalinity. Temperature swings, pH shifts, lighting issues, to name the ones off the top of my head. I recently lost all my SPS except 4 pieces. I do have one coral that RTNed half way and stopped, and I've been debating cutting off the skeleton half, and running a bead of superglue around it. I had a colony that survived for sometime with some branches RTNed and some not, but eventually the rest RTNed. I'm tagging along for Kevin's advice...

 

[wrightme43]

I had that happen to a cool blue acro. I fragged and it has recovered well, the frags are incrusting, and sending out new growth fronts. It worked for me.

 

[-=dieseldave=-]

I wonder if a big ball of slime from one or all the 4 new Acros landed on the RTNed coral and was not removed due to lack of flow on the RTNed coral or the slime was super toxic.
If this it the case fraging off the live branched is up to you. I don’t know if it will speed up the recovery, or not. It will look better if you keep what lived and toss the dead branches in your sump. You might wand to give a frag to someone you know just incase you lose the rest of the Acro.

 

[jetaero]

I personally think there is more to it than just calcium and alkalinity. Temperature swings, pH shifts, lighting issues, to name the ones off the top of my head. I recently lost all my SPS except 4 pieces. I do have one coral that RTNed half way and stopped, and I've been debating cutting off the skeleton half, and running a bead of superglue around it. I had a colony that survived for sometime with some branches RTNed and some not, but eventually the rest RTNed. I'm tagging along for Kevin's advice...

I completely agree nikki, for some reason I had thought they would be ruled out. :\ *slaps his neptune for making him not check*

-Josh-

 

[MarineDreamer]

“It is my strong opinion that RTN will prove to be synonymous with shut-down reaction (SDR), described on page374. In my view, RTN does not represent a new disease but rather is very likely to be, at least in part, a response to stress. It is possible, in fact, that this response results in self-rejection or autolysis-the digestion by the coral of its own tissue.”

“It is also suspected that histoincompatiblity following the addition of new coral specimens to established systems may be a key stressor in producing the reaction in certain instances. The ability of corals to detect “self” and “non-self” is very acute, and copious numbers of as-yet-unidentified allelochemical, allomone, and pheromone markers, including glycoproteins and toxic organic compounds could be involved.”

Eric H. Borneman, Aquarium Corals: Selection, Husbandry, and Natural Selection, T.F.H Publications, Inc, Page 382

Given the circumstances surrounding my RTN event and that none other of the established corals are exhibiting any tissue loss, recession, or a reduction in polyp expansion, including other Acroporids in the system, I’m inclined to disagree with the opinion that this maybe related to a water quality issue.

I wonder if a big ball of slime from one or all the 4 new Acros landed on the RTNed coral and was not removed due to lack of flow on the RTNed coral or the slime was super toxic.

So the nod goes to dieseldave, though I would think that in closed system, especially in my tinny tiny 55 gallon, which “a big ball of slime” or even a little one for that matter, would have to physically land on the colony to invoke a response.

-Sigh- All that having been said, it seems that popular opinion has me fragging the good branches out in the hopes of holding out from Nikki’s experience of having a colony seemingly on the edge of recovery only to lose all on its tissue in the future. This is not the way I wanted to learn how to frag out my corals.

Thanks to everyone for sharing their opinions, thoughts, and experiences.

 

[Anthony Calfo]

I'd frag away only the best (most seemingly stable, unafflicted) branch tips... and then please(!) learn to appreciate and use quarantine proceedure for all new livestock without exception my friend! Truly It pains me to see aquarists struggle and animals die due to the game of russian roulette that we/you play every time to place something wet into your aquarium without home-based and supervised QT.

I have links to fav QT discussions/articles in my stickied list of fav links in my forum.

QT and you should have little to no fear of spreading acro bugs, RTN, flatworms, etc.

 

[kevinpo]

Hello,
I would frag the remaining branches cutting off about 1/4" of good tissue.

Even with good quarantine practices SPS corals can RTN but at least with quarantine you can reduce the chance of disease/parasites as the culprit.

I have witnessed the reaction of resident corals to the addition of a new coral. They are very aware of who their neighbors are. I have seen a Platygyra extend 12" sweepers just seconds after introducing a new coral in a 650 gal system. Wild colonies on average seem more sensitive to additions of new corals. I do not consider a coral to be a long term resident until it's in the tank for a couple of years.
I can't say I've seen RTN as a specific disease (doesn't mean that it does not exist just that I have not seen it) but rather as a reaction to environmental condition(s).

Regards,
Kevin
PS: I'm honored to have Anthony post here and appreciate his advice/comments

 

[damien_kee]

suggest u to frag it.... cant save the colony but save the species....

 

[Anthony Calfo]

the pleasure is mine Kev... truly. I just regret I have not won the lottery yet and cannot read more sites/forums like yours at greater length

 

[mojoreef]

RTN is more of a corals reaction to enviromental impacts, From my readings and experence its do to a enzyme release with in the coral that causes the game to start, simular to a bleaching event with heat stress enzymes.
As mentioned by others fragging is usally the only route out. It the pic of the coral you posted I would just toss that one, to far gone. Another thing that has worked for me is to frag the coral and coat the bottom tissue in crasy glue, it has stopped RTN a few times for me.


Mike