The origins of rapid tissue necrosis (RTN)

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Hey everyone! I recently stumbled across this channel on youtube (Prime Coral). On this channel the guy appears adamant that he has found one of the root causes of RTN in corals (sps and lps alike). He claims that it is Philaster, a marine protozoa that enters the corals via their mouth and consumes them from the inside out. The channel has gone MIA recently and I would love to see some concrete results and conclusions regarding the origins of RTN. I seen few people in the reefing community bring this up as a topic of discussion so I thought I would reboot the conversation surrounding this.

They do have a website where they advertise a dip that kills these protozoans along with a myriad of other common coral pests as well, such as black bugs, aefw, etc.

*Disclaimer*
I am not affiliated with this channel, nor person. This is not an advertisement for their product in any manner. I'm just a curious reefer that wants to learn and study more about the complex ecosystems in our reeftanks.

Here is his website, here you explore his methodology, products, and his insights on the cause of RTN/STN
https://coralrtn.com/

Here is his quick introductory video on the parasite.

Here is another video documenting a heavy infection of Philaster


I have been wondering about the causes of RTN and STN in corals ever since I've began the hobby. Even when components such as water chemistry, lighting, and flow appear to be perfect there's still that small off chance that you lose a coral randomly. In some cases I think it could be related to bacterial imbalances in the aquarium microbiome, or pure ignorance/ poor husbandry, but these videos appear to show a link between RTN and these Philaster protozoan.
I feel that it would be easily to detect if one has these protozoans in their system as they seem to proliferate extremely fast and systematically find new host corals to infect. This leads me to think that if introduced to an extremely dense tank these protozoans could wreak havoc incredibly fast as they infect everything in the system. So it might be cause of all random RTN/STN but it could be a large proponent related to the issue.

Has anyone had any experience with these pests before? I'd love to hear from others regarding this, as this could be the next barrier we cross in reefkeeping where we can now properly identify the pests that cause RTN.

I'm still open to the plausibility of certain strains of bacteria causing RTN/STN but there has not been anything concrete regarding what type mainly affects acropora and how to treat the issue. According to my research, a certain strain of vibrio and arcobacter seem to be cause in the wild and in captivity.
Amoxicillin and ciprofloxacin have had some success in treating RTN in ailing corals, but I am worried about the improper use of antibiotics and the possibility of creating antibiotic-resistant bacteria that could possibly cause horrible repercussions in the future.

I'd would still love to hear more about people's experience with antibiotic use in their tanks or as a possible dip for ailing corals and if it successfully treats RTN in corals. If so, it may still prove a valuable tool in our toolbox.

These philaster protozoans might not be the root cause of RTN, but their presence, along with pathogenic bacteria, and other coral stressors might be a crucial catalyst when it comes to RTN/STN and the sudden and random loss of coral.

I'd love if the reefing community could come together and discuss this topic in a civilized manner to progress our hobby. All thoughts and experiences should be met with proper respect and critiques, flat out denial and inflammatory accusations get us nowhere.

Here are some previous thread on various forums discussing this topic for those who are curious.

https://marsh-reef.org/index.php?threads/cure-for-stn-rtn-finally.59155/page-1

https://www.reef2reef.com/threads/possible-solution-to-end-rtn-forever.563527/




As always, Happy Reefing!
 
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sculpin01

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Ciliated protozoa can be treated with metronidazole (which is effective against anaerobic bacteria and protozoans). In addition, there’s a thread in the research forum on using clove oil for treatment of ciliated protozoans.

I have done both with some success, most recently on a frag that arrived in yellowish water with tissue rapidly stripping off. I dipped said frag in the clove oil dip for ten minutes with zero expectations of success. Put it in an area of low light and flow. Shockingly, two branch tips survived and are now completely healthy looking.

Similarly, I used a metronidazole dip on a frag of A. monticulosa that unexpectedly started losing tissue with similar results. Said frag has now regrown almost all of its skeleton.

I’ve considered doing a combination metronidazole/clove oil dip but am not certain if that would work as the metronidazole may partition into the clove oil.
 
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Ciliated protozoa can be treated with metronidazole (which is effective against anaerobic bacteria and protozoans). In addition, there’s a thread in the research forum on using clove oil for treatment of ciliated protozoans.

I have done both with some success, most recently on a frag that arrived in yellowish water with tissue rapidly stripping off. I dipped said frag in the clove oil dip for ten minutes with zero expectations of success. Put it in an area of low light and flow. Shockingly, two branch tips survived and are now completely healthy looking.

Similarly, I used a metronidazole dip on a frag of A. monticulosa that unexpectedly started losing tissue with similar results. Said frag has now regrown almost all of its skeleton.

I’ve considered doing a combination metronidazole/clove oil dip but am not certain if that would work as the metronidazole may partition into the clove oil.

What were the products that you used for the metronidazole and clove oil? Also what was the formula for the dip?
 
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ScottB

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I recall the guy behind this product. I met him once at MACNA 2019 and talked with him after having read a few exchanges here on R2R. Those exchanges didn't go well from a PR perspective for him. He was equally defensive / hostile in person. I am a very chill and curious guy. I just asked his take on the seemingly reasonable debate around whether philaster are the cause or the effect of STN/RTN. His answer was essentially "you are an idiot who spends too much time on the internet." I answered "One or both of those assertions may be true. Can we go back to my question about how one proves which came first?" He felt he didn't need to explain or prove anything to me, as I am not a trained scientist. Mokay.

My default focus for fish & sticks is the same: build and maintain immunity. There only two predators I go after fanatically: red/white/black bugs (tegastes?) and AEFW.

And yes, I have STN come and go all the time. Not continuously of course, but it is a fact of life in my two systems.
 

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For metronidazole I add sufficient powder to achieve saturation in a beaker of 500 ml of tank water. Solubility isn’t great, so it doesn’t take much. DMSO can be used to more effectively get it into solution if you want but I don’t do so. I use API General Cure or Metroplex. If I am concerned about bacterial infection, I will add amoxicillin (general antibacterial action) and doxycycline (API Fin&Body) for rickettsials.

I just follow the recommendations here:

In terms of causative organism vs detrivory, Dr. Michael Sweet wrote two articles on ciliates suggesting that they act with an additional bacterial infection to cause white syndrome/RTN.


 

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This is old news... He is a snake oil salesman. Junk science, and just trying to make a buck off of unsuspecting hobbyists. Ara Deukmedjian is his name and he is a neuro-spine surgeon. His product killed many fish and crashed quite a few tanks... Look elsewhere for true solutions to RTN/STN.
 
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I recall the guy behind this product. I met him once at MACNA 2019 and talked with him after having read a few exchanges here on R2R. Those exchanges didn't go well from a PR perspective for him. He was equally defensive / hostile in person. I am a very chill and curious guy. I just asked his take on the seemingly reasonable debate around whether philaster are the cause or the effect of STN/RTN. His answer was essentially "you are an idiot who spends too much time on the internet." I answered "One or both of those assertions may be true. Can we go back to my question about how one proves which came first?" He felt he didn't need to explain or prove anything to me, as I am not a trained scientist. Mokay.

My default focus for fish & sticks is the same: build and maintain immunity. There only two predators I go after fanatically: red/white/black bugs (tegastes?) and AEFW.

And yes, I have STN come and go all the time. Not continuously of course, but it is a fact of life in my two systems.
Yea, same here Scott. My qt protocol targets those pests as well, multiple KCL dips and Dr. G in tank treatments seems to catch all of the nasties that are typically involved with acros. I'm still curious on the relationship of these philasters and bacterias. It would be awesome if someone with more first hand experience would chime in.



This is old news... He is a snake oil salesman. Junk science, and just trying to make a buck off of unsuspecting hobbyists. Ara Deukmedjian is his name and he is a neuro-spine surgeon. His product killed many fish and crashed quite a few tanks... Look elsewhere for true solutions to RTN/STN.
This seems to be the gist that I'm gathering. The person might not have been the best to deal with but I wonder if he was onto something. Could you elaborate on the tank crashes? Were they the result of in tank treatments or dips? RTN/STN seems to be more prevalent in more recent imports rather than aquacultured/older pieces in my experience (given optimal conditions).
 

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Yea, same here Scott. My qt protocol targets those pests as well, multiple KCL dips and Dr. G in tank treatments seems to catch all of the nasties that are typically involved with acros. I'm still curious on the relationship of these philasters and bacterias. It would be awesome if someone with more first hand experience would chime in.




This seems to be the gist that I'm gathering. The person might not have been the best to deal with but I wonder if he was onto something. Could you elaborate on the tank crashes? Were they the result of in tank treatments or dips? RTN/STN seems to be more prevalent in more recent imports rather than aquacultured/older pieces in my experience (given optimal conditions).
I can’t remember if it was on this site or on Facebook, but several people who used his product which was supposed to cure RTN and STN lost all of their fish due to a rapid decrease in oxygen levels and this created a snowball effect causing the tank to crash. It was a few years ago but you might find more information either searching here or searching Facebook or both.
 

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I believe the general consensus is that The philasters are a scavenger that show up once the damage is done, and not the actual cause.
 

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Regardless of all of the above (which I do not disagree with at all), "RTN" and "STN" aren't specific diseases to be cured, they are descriptions of how a disease (or parasite, infection, etc) affects a coral - quick deterioration or a slower process. Both can have many causes
 
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Regardless of all of the above (which I do not disagree with at all), "RTN" and "STN" aren't specific diseases to be cured, they are descriptions of how a disease (or parasite, infection, etc) affects a coral - quick deterioration or a slower process. Both can have many causes
Right on, I completely agree. These generic terms don't quite specify the cause of the corals dying. Corals can be stressed by a myriad of things (poor water chemistry, flow, pests, shipping, lighting, etc).

To be more specific I was more interested regarding the microorganisms that cause corals to RTN in relatively pristine and established SPS systems where none of the typical pests are present (AEFW, blackbugs, redbugs, etc). Which specific strains of bacteria have been identified to stress corals and how do we treat for them. I see that cipro, amoxicillin , and erythromycin have been used successfully to treat Brown Jelly Disease in LPS primarily but not a lot has been reported about their efficacy regarding SPS corals.

 

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This is old news... He is a snake oil salesman. Junk science, and just trying to make a buck off of unsuspecting hobbyists. Ara Deukmedjian is his name and he is a neuro-spine surgeon. His product killed many fish and crashed quite a few tanks... Look elsewhere for true solutions to RTN/STN.
Seems odd a Neuro/spine surgeon would need to make a buck of reef hobbyists.
 
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I am curious about how these diseases start at the base of the colony and work to kill it from the ground up. How come they don't ever work top down? The colony is a group that originally started from one cell, (or a few cells from a frag start) but how come the bottom dies first? If it was disease driven wouldn't we expect the colony to occassionally rot from the top down? I don't have an answer, just wanted to put that thought out here.

@Gatorpa -Med school is expensive and student loans are killer. Same with this hobby. Even doctors get hooked on frags? :)
 
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I am curious about how these diseases start at the base of the colony and work to kill it from the ground up. How come they don't ever work top down? The colony is a group that originally started from one cell, (or a few cells from a frag start) but how come the bottom dies first? If it was disease driven wouldn't we expect the colony to occassionally rot from the top down? I don't have an answer, just wanted to put that thought out here.

@Gatorpa -Med school is expensive and student loans are killer. Same with this hobby. Even doctors get hooked on frags? :)

I've seen RTN start from the middle of a colony and sometimes from the tips as well.
However, most of these cases I've attributed the cause to be shipping stress as these pieces died immediately after I received them. I rarely see established corals RTN from the tips, in the cases where the tissue begins to recede from the tips the water chemistry is usually to blame in my experience.

I think the predominant reason the corals die from the base up could be related to detritus buildup around the base of the coral. This dirty detritus is probably a breeding ground for pathogenic bacteria and they work their way up the weak coral from there.
 

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Beyond the questionable Philaster treatment above, I think it might be interesting to pool cases of successful recovery from RTN and STN and what methods were used. Perhaps a dedicated thread with pre-, post-, and recovered photos with whatever methods were utilized. The idea being that even though it is a multifactorial disease(s), we (the reefing hivemind) may be able to see trends towards responses to certain approaches.
 
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Seems odd a Neuro/spine surgeon would need to make a buck of reef hobbyists.
Also seems odd to use the Dr. title to imply that you are a marine aquarium expert when your training has nothing to do with marine aquariums. Very shady! He gave it his best shot. Mo money mo problems
 

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Also seems odd to use the Dr. title to imply that you are a marine aquarium expert when your training has nothing to do with marine aquariums. Very shady! He gave it his best shot. Mo money mo problems
I find anyone with a phD loves to promote that title….
 

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I find anyone with a phD loves to promote that title….
I have a phd
F9E8A4F3-D37B-4C01-9A58-142697BFB997.jpeg

I have dug a lot of post holes with it in my back yard and for my neighbors and last year I replaced a sign that got pulled out of the ground when a contractor tied off an oil boom that pulled the concrete anchor and post out of the ground as the tide rolled in.
 
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I remember the philaster debacle. What I kept thinking (and I think the general consensus) is that the philasters being touted as the cause of R/STN were more likely to be opportunistic feeders on the dying tissue rather than the cause of it. The science wasn't sound IMHO.
Beyond the questionable Philaster treatment above, I think it might be interesting to pool cases of successful recovery from RTN and STN and what methods were used. Perhaps a dedicated thread with pre-, post-, and recovered photos with whatever methods were utilized. The idea being that even though it is a multifactorial disease(s), we (the reefing hivemind) may be able to see trends towards responses to certain approaches.
I do agree that this could be beneficial. :)
 

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I think the loss of tissue is due to Philaster, but it requires the pre-existing injury of said tissue by a polymicrobial bacterial infection. Stopping Philaster slows coral death but does not stop it. To stop coral death, antibiotic therapy is required. The second paper I linked to demonstrates this without question.
 
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