Types of RTN???

[Kerbash]

Hey guys,

No picture but just a thought that crossed my mind today. Not sure how accurate this is but thinking about my past experience I think there are a couple of different types of RTN and how to treat them seems different. Would like to hear about anyone thought or input! Or if you have any experience confirming/contradicting any of my experience please post!

Observation:

1. Brown Jelly:

- Noticeable especially in low flow area

- Flesh inflates into a brown jelly

- Seems to spread from proximity

- No apparent reason for occurrence

- Seems to always stop after iodine dip ime

2. Peeling off:

- Flesh falls off as sheets

- Most prevalent in Pocilloporidae (birdsnest, stylo, etc)

- Only happened three times for me so far in separate colonies: twice alk too low, another got stung by hammer, both times, manage to save frags for both.

- Cut above the line, if far enough works 100% of the time

3. Burnt tips:

- Corners and tips of acros turns white

- Diffused (no clear distinct line separating healthy flesh)

- Mostly in acropora, birdsnest and monti

- Seems to be due to unstable param??? No clue

- No concrete cure, sometime fragging work sometime it doesnt

4. Distinct Boundaries:

- Patches of flesh necrosis

- Clear distinction between dead and living flesh

- Mostly in acropora, monti

- No clue, possibly irritation? Happened a few types never any link to each other.

- 50/50 cure with antibiotics for 10 days. Fragging works some time as well.

Hypothesis

Brown Jelly: I am pretty sure this is caused by some pathogen, they seem to kill really rapidly, I have never seen any progression or where they start because by the time I notice, half the colony is gone. Dips seems to always solved it for me in SPS. Also not sure is it the same in LPS but peroxide treatment in LPS seems to work 80% of the time if caught early enough, to nervous to try on SPS.

Peeling off: Never seen acropora do this but it might be because they are all in high flows so any flesh gets blown off before I can see. A wild theory here, but I think it seems that this maybe due to some anchoring/calcification mechanism getting broken, so the flesh slough free from the skeleton, not sure what triggered it sometime, but the two out of three times that it happened its because of low alk. The rest of the colony never looked distress, polyp extension like normal.

Burnt tips: Seems to always be related to unstable param, No clue why pass that though could be because of a curse for all I know 😅 

Distinct Boundaries: I think its due to some pathogen distinct lines of dead coral seems to match some known coral disease although all of those are STN i think. Viral is possible too, thats why antibiotics and dips only works sometime.

Note: Although I had all of these happened out of no where, stress of some sort seems to be a trigger for any of these.

[Eatfrenchfries]

Brown Jelly: bacterial imbalance that can rampage through coral tissue rendering the zooxanthellae inside a gelatinous blob. It is thought the the bacteria responsible exists in all corals but stressors in the environments can shift in their favor. This imbalance may not directly impact harm the coral but it will exacerbate any underlying issues further worsening the situation.  Bacteria are extremely hard to combat (certain sponges are critical to regulating them, in a healthy reef these should develop in time based on the situation). The dips we use often require the coral to be healthy enough which in the case of SPS which have almost no tissue is an already uphill battle.  Capable of jumping to neighboring corals in the same family. Hard to say if bacteria linked to different areas of collection have to play into different variations of this disease. (Example: Aussie vs Indo LPS being affected by different pathogens, I recall a large # elegance corals being wiped out a few years back from Indo). Antibacterial dips might help but once brown jelly is caught in a tank it is best to enforce isolation measures to preserve the rest from succumbing. 

Peeling Off: Polyp bailout / shedding of the skin is never good as it is a last ditch attempt to living tissue in hopes of inhabiting another coral of the same family or restarting itself elsewhere in a calmer environment. Fragging healthy bits might work if the piece is large enough to operate on its own without drawing on too much via connective tissues (chunks > frags). High phosphates can inhibit Alk and Ca consumption stunting skeletal growth. If a coral is not growing then something is wrong especially in fast growing corals like SPS. Coral that stops growing its skeleton either has to start throwing away tissue or find a better option. If the tissue is growing faster than the skeleton it'll brown out and also potentially bail itself (hard to control how much tissue to bail on acros when there is not much tissue). 

Burnt Tips: Usually related to stunted growth because I am missing something from my reef whether it be trace elements, maintenance, water change, etc. Just that one thing I forgot to do to keep it growing will result in burnt tips. This relates back to the skeleton being exposed at the tips because the tissue lacks nutrients to cover it. Exposed skeleton is prime real estate for everything you do not want to be competing with your coral. Also easy access to the inner porous material.

Distinct Boundaries: coral necropsy of skeletons can leaves cells behind. Skeletons high in dead bacteria (more bacteria comes in to eat the dead cells which just adds to the competition) take longer to be recolonized by the coral which opts to just grow in a different direction instead. 

 

RTN/STN is a heavily detailed topic. There are lots of ways to look at it. Stress for sure is the start of all these issues but the health of your reef will be the best remedy. My belief is that the bacteria populations change hands as different levels of various organic carbon sources build up in a reef tank. *Bacteria are not the direct cause of necrosis issue but just adding more fuel to the fire. In the ocean a reef ecosystem has multiple layers to handle all of its dirty business. Each layer houses micro fauna capable of handling certain events. If the event is more likely to occur then chances are the ecosystem will have some deposit built up to handle it. In a tank the ecosystem you built will

1. handle it biologically on its own (ugliest option......maybe)

or

2. your input will handle it (tortoise or the hare)

or

3. your ecosystem has reached succession (and not the level you want but a step or two after). 

P.S. I use a vortex diatom filter to reset my tanks from time to time. Helps deal with issues from established reefs leading into old tank syndrome. 

[obrien.david.j]

I don't have any experience with brown jelly, nor elegance coral disease, but I have extensive RTN/STN experience in Acros over the years.    

I'm impressed with the progress in the hobby overall, especially pointing to bacteria as the source of many of these.   My mental model is it's like human health.   I can be exposed to something, and if I'm stressed/immune compromised I'm most likely to catch it.  If I'm in peak health, I'm less likely to catch. But no guarantees.

I used Oxolinic Acid successfully in my most recent RTN incident.  No adverse effects since then.  And tank has never looked better.   

Although it's 2+hrs long, it's got a good conversation where this came from - and it talks about brown jelly and elegance coral diseases.

 

 

 

 

[Manny Tavan]

I’ve seen two types the RTN. The “I don’t know why this is dying” and the “I really don’t know why this is dying”