What cause RTN ?

[Ralphyhp]

Hi friends, i loose one of my favorites Acro.today . Whats mean RTN, did any can explain me what can cause a RTN on SPS. This is the first time i loose a SPS for RTN, for that reason i never worried about the meaning of this sickness, i only know that RTN use to bleach the corals. My tank water parameter are as fallows: Ph- 8.0 to 8.2, Amo, Nitri, Nitra, Phos are O , Calcium 450-500 ppm,Spec. Gravity 1.025, temp.78g F. I use RO/DI , Calcium reactor, my lights 3 250w 10000k Ushio, 2 140w Uri actinics and two 50/50 65w Hamiltons PC. On Sunday at the morning i present some temp. problems on my chiller because i was installing a new fan cooler to it and the tank temp. raise for a temp. of 91g F i finally fix the chiller on Monday at 1:30 pm. My tank run on a entire day without lights and on a different temp. parameters. Can this cause this RTN problem? Any way tonight i going to do a search on RTN at reefs .org library. Thanks in advance for any help. Here are some pics of the SPS. Ralphyhp :wink:

 

[Ralphyhp]

RTN- Rapid Tissue Necrosis. :lol:

 

[Len]

RTN can be attributed to several things, usually bacteria (Vibrio suspected) or protozoans. Once they take hold of a coral, it doesn't take long for the whole coral to succomb. Once you see something like this happen, best thing to do is frag off an uninfected area to regrow. Some people suggest that iodine dips help as well, although it's never worked for me.

4 or 5 years ago, there was mass RTN cases during the summer that had everyone in a panic. Vibrio was the bacteria of the discussion that year.

Sorry to hear about your loss.

 

[brandon4291]

I have induced standard tissue necrosis in my reefs by letting the temp get that high. IIRC the RTN as Len said would be attributed to an infection or infestation, whereas non-RTN tissue necrosis or recession can be attributed to high temp physically killing the flesh, or too much current stressing it and peeling it off, or insufficient Ca+ Alk measures to support plating and healthy growth. In your case I do not suspect RTN, I suspect standard necrosis and/or recession. Fix that temp as you said and all will likely be fine...

B429

 

[brandon4291]

Incredibly beautiful tank and pics btw, sorry for your loss. That green 'bush' would go for $100 down here in cotton country Tx.

B

 

[Anonymous]

So far, the aggressor in RTN remains unidentified. More than likely it will prove to be programmed cell death/apoptosis. Bacteria are likely incidental to the cell death.

 

[brandon4291]

Galleon, you know how they (?) were attributing bleaching and RTN events of wild acroporid fields (Fijian I believe?) to the global warming, I wonder if the warming causes the tissue recession through physical stress and then bacteria get a foothold and continue out the recession/necrotic event until they are totally dead? Just wondering

B

 

[Ralphyhp]

Len for me your work on reef.org are outstanding, you always take part of any discussion i gave you an A+. As Brandon saids, I wonder too if this RTN event is caused for the high temp. and the photoperiod change, causing a stress on all my corals. After that this coral start the RTN. I have a super giant Lether coral on this tank and after that temp. change, it reduced on it size too. I use to frag any of my colonies when i bought them, so i have another of this colony :wink:. I have another colony with few branches bleaching, but in this case is because i place this one on a heavy current as Brandon saids, the current are stressing it and peelling it off. Brandon 6 month ago this colony cost me $50.00 at my LFS but it growth about a 2". Thanks Everybody, Ralphyhp :wink: .

 

[LauraH]

Ralphyhp,

That was depressing. What a beautiful piece that Acro was.

Have you considered installing canopy fans and possibly a fan constantly blowing on the sump in order to keep your tank temp stable and less reliant on one piece of equipment (chiller)? This would lessen the chance of something like this happening should the chiller fail. I used to depend on a chiller until mine broke. I installed the fans and discovered that I really didn't need the chiller at all. Of course, I have air conditioning in my house, so that makes a difference.

 

[Ralphyhp]

Laura thanks a lot. I have 4 fans on my canopy. I need one for my sump, what kind of fan you use to use on yours, Thanks again, Ralphyhp. Ps. Laura if you like that pics. take a look to this one, this are one of my fav. pics.

 

[mehdirah]

Hello,
I had the same problem with a purple acropora last week: temp went up to 89°F for a day (I has no chiller as it was not necessary until that moment). RTN begain as a small patch. The next day, temp was down to 85°F, and the following day I bought a chiller and temp when to 79°F. At this moment, the small white patch had already extended to all the coral except 1 inch at branches extremities. Which finished dying in the 3 next days even if the temperature was now under control with the chiller.

In my case: the problem was clear, too high temperature for only 2 days! I tried an iodine bath the second day, but it didn't changed anything.

At leat, the rest of my animals didn't suffer at all.

Morale of the story: I should have bought the chiller sooner!

 

[klingsa]

I believe, from the literature research that I've done for two major papers on this subjec (the first one was on bacterial causes of coral bleaching), bacteria are oftentimes the cause of a bleaching event. That doesn't mean, however, that increased water temperature is not also a cause. It has been shown to lower the resistance of the coral to bacterial infection, allowing the bacteria to outcompete the coral. Saying that increased temperature CAUSES coral bleaching is not very descriptive...the temperature must affect some aspect of coral (or zooxanthellae) physiology. There are all kinds of theories on what that affect might be. I'm out of town and don't have my research with me. If anyone is interested, I can post some of the information I found when I get home on Monday.

It seems to me that RTN is the end result, and not a very good description of the cause or process involved. I mean, I know it is a recognized phenomenon...does anyone know the exact definition? If the cause is truely unknown, then how can we differentiate? It seems that anything which causes coral death could be considered as tissue necrosis, like silt deposits from river deltas. That keeps the coral from getting the light it needs, of course, which will cause tissue necrosis.
Thoughts?

Sara

 

[Anonymous]

The bottom line is: no one really knows. There are several "theories" but no one can prove RTN is attributed to temp, bacteria, etc...

Sometimes it's just time to go. In my experience, RTN occurs when coral is subjected to poor water quality or poor treatment as in a transfer from a tank where things weren't all that well to another. I guess stress is a main ingredient.

Usually, a tank with high water quality: no detectable phosphate, nitrate, etc... that has an acceptable ionic balance of calcium, magnesium and the myriad traces elements where pH and alk stay within an acceptable range, does not "usually" experience RTN events.

I do notice in your photos that there is a little bit of stinging going on with the frilly mushrooms anf the SPS. Sometimes a sting is all it takes.

Keep in mind, I am as full of crapola as the next guy. I know what works for me: outstanding water quality and a very hearty and large refugium.


Snapper

 

[LauraH]

Ralphyhp,

The fan is a mountable plastic fan about 12" in diameter. I don't remember the name, but I got it at Walmart for about $10. You can mount it right to the inside of a wooden cabinet stand and position it any way you wish. It really helps with evaporative cooling.

Nice pic. You've got some great color in your SPS.