A possible biological way to decrease/fight RTN

[Lasse]

This may be published in wrong forum - Admin - move it if this is the case.

RTN in branching stony corals have been partly associated to bacterial activity. In a recent study - posted late February this year - researches found some evidence that bacterial/microorganism activity can be a at least one reason for RTN. They also found a possible explanation why RTN can be common in the wild nowadays. Maybe some of us have to rethink when we stock our aquariums because they found that a lack of cucumbers can be one reason for RTN in frags from Acropora pulchra planted in the wild.
From the article

Here we show,via field manipulations in both French Polynesia and Palmyra Atoll, that historically overharvested sea cucumbers strongly suppress disease among corals in contact with benthic sediments. Sea cucumber removal increased tissuemortality of Acropora pulchra by ~370% and colony mortality by ~1500%.Additionally, farmerfish that kill Acropora pulchra bases to culture their algalgardens further suppress disease by separating corals from contact with thedisease-causing sediment—functioning as mutualists rather than parasitesdespite killing coral bases. Historic overharvesting of sea cucumbers increasescoral disease and threatens the persistence of tropical reefs. Enhancing seacucumbers may enhance reef resilience by suppressing disease.

The article as PDF

Sincerely Lasse

 

[Reefering1]

Interesting.. so it sounds like it would be of benefit to have cucumbers in the tank(?) I didn't read the full article, but is it a specific type of cucumber?

 

[Tavero]

This may be published in wrong forum - Admin - move it if this is the case.

RTN in branching stony corals have been partly associated to bacterial activity. In a recent study - posted late February this year - researches found some evidence that bacterial/microorganism activity can be a at least one reason for RTN. They also found a possible explanation why RTN can be common in the wild nowadays. Maybe some of us have to rethink when we stock our aquariums because they found that a lack of cucumbers can be one reason for RTN in frags from Acropora pulchra planted in the wild.
From the article


The article as PDF

Sincerely Lasse

I've seen several forum posts where sea cucumbers caused a tank crashed so I don't think that's the solution.

But UV lights should be a lot more effective in controlling bacterial density and a good substitution to cucumbers.

This research is more relevant for natural coral reefs instead of reef tanks.

 

[Lasse]

I've seen several forum posts where sea cucumbers caused a tank crashed

This normally the Sea Apple that does these crashes and they filtrates the water - not the sand. However they are classified as sea-cucumbers and this have create the confusion that sand shifting cucumbers can cause crashes - IMO. I have had the tiger tail sea cucumber ( pictures) in my present aquarium (8 years old) - they have both died and propagate without any crashes.

A sea Apple (pictures) filtrate the water in the same way as UV-C does - not the sediment/sand. IMO both the Sea Apple and UV-C is not very good in order to control the microbial life in sediment/sand. However - most of the other sea cucumbers filtrate the sediment/sand and are - IMO - harmless according toxicity - Live or dead. At least in my aquarium and the tiger tail sea cucumber.

You have seen posts and I have had sand shifting cucumbers and we have opposite thoughts. In my last work we had the black sea cucumber for many years (and they still have) without any problems.

Sincerely Lasse

 

[Tavero]

This normally the Sea Apple that does these crashes and they filtrates the water - not the sand. However they are classified as sea-cucumbers and this have create the confusion that sand shifting cucumbers can cause crashes - IMO. I have had the tiger tail sea cucumber ( pictures) in my present aquarium (8 years old) - they have both died and propagate without any crashes.

A sea Apple (pictures) filtrate the water in the same way as UV-C does - not the sediment/sand. IMO both the Sea Apple and UV-C is not very good in order to control the microbial life in sediment/sand. However - most of the other sea cucumbers filtrate the sediment/sand and are - IMO - harmless according toxicity - Live or dead. At least in my aquarium and the tiger tail sea cucumber.

You have seen posts and I have had sand shifting cucumbers and we have opposite thoughts. In my last work we had the black sea cucumber for many years (and they still have) without any problems.

Sincerely Lasse

Well I think, the issue is making sure to introduce the the non toxic instead of the toxic one. And wrong identification may lead to a tank crash.

Do these ground dwelling cucumbers reduce detrius.

 

[ISpeakForTheSeas]

With regards to sea cucumber toxicity:

from what I’ve read, it seems literally all sea cucumber (medusa worms included) do have the toxins you’re concerned about to some degree or another. The part that’s hard is that how much toxin the cuke contains and how likely a cuke is to release those toxins varies from species to species. Some species are substantially more prone to releasing the toxins than others, and some release a good deal more of the toxin than others. An important note here, the toxin of sea cucumbers (holothurin) is an ichthyotoxin (it primarily affects fish, though in high enough quantities it can affect other things like inverts and people too), so if the cucumber does release its toxin into the tank, the inverts might be fine. For more info, here’s a post I made referencing and expounding upon another of my posts on the subject from a while ago:


As mentioned, many sea cucumbers will release toxins when stressed/dying, so it's important to keep them happy and to be prepared to deal with that situation should it arise (i.e. be prepared to do an emergency water change, add carbon, transfer livestock to a hospital tank, etc.) - some cukes are highly toxic, some only mildly, some release toxin when stressed, others only release it once their corpse starts to decay, etc. so the risk varies a lot depending on the species, but unless they're one of the highly toxic species (like Sea Apples) it's not usually too big of a concern. Plus, many species will give warnings that they're dying/stressed, so sometimes people are able to get a heads up that they need to remove them

A lot of sea cucumbers will give you some sort of warning before they die (such as contracting to look short and squat - a defense mechanism/sign of extreme distress that they use to try and escape predators/death - or ejecting a cloud of toxins - because of how this actually works, the cucumber generally dies after releasing the toxins), and some of them, as long as they don't get hyper distressed, (as I understand it) won't intentionally release toxins in your tank - they just die like a normal animal, so as long as you remove the body fast enough, it won't poison your tank.

Yeah, I've only heard of a couple of instances where a "cuke nuke" actually took place despite knowing multiple instances of cucumbers ejecting either a toxic fluid, their organs, or their cuvierian tubules, so it's definitely not a common event (at least not with sand sifting species). That said, keep in mind that the toxicity varies from one species to the next, and some species are more toxic in certain ways (some are more toxic when they expel toxins in some way, others contain more toxin in their body wall, etc.), and various circumstances (such as water volume, skimmers, running carbon or not, etc.) about the aquarium they're in can determine how much harm the toxin causes.

Personally, I'd say they generally seem pretty safe, but you need to be aware of the (relatively low) risk and have a plan in place to handle it if things go awry.

The cuke nukings:

EMERGENCY - Anemone Toxin / Sea Cucumber Toxin

Hi! Unfortunately, this morning I woke up to all my fish deceased, the sea cucumber and anemone also dead, with some gooey like slime stuck in my return pump. All of my crabs and snails are alive including my pom-pom, Anemone Crab and my Conchs, critters I thought to be extremely sensitive...

www.reef2reef.com

https://www.sciencedirect.com/science/article/abs/pii/S1557506321000483

An instance of ejecting a fluid (nothing seemed to have been harmed in the tank, but this stuff is reportedly toxic):

EMERGENCY - New Black Sea Cucumber Red Stuff

Hey all, I recently got a black sea cucumber. I acclimated it with the drip method, and after a day it is now expelling this stuff. I've ready a lot about the toxicity, but I'm not sure if I should pull him now or not. All my SPS and fish seem to be fine.

www.reef2reef.com

 

[Lasse]

Do these ground dwelling cucumbers reduce detrius

They eat organic detritus including bacteria living on the detritus.

I have the tiger tail cucumber in my aquarium - 80 G - IMO - the others get to large for my aquarium. I see them now and than. Have not have any issues that I can link to them. IMO - they do so much good things in my aquaria that I can live with the small risks that @ISpeakForTheSeas mention. I have similar experiences with the large black one from my former work. In aquarium like mine - there I want to mimic a natural reef as much as possible - they are one of the pillars in order to have a good CUC (Cleaning Up Crew).

Sincerely Lasse

 

[Big E]

Keeping a sand bed clean is probably a more direct way to look at this. If it's conches, fish, you stirring/vacuuming, or a cucumber it would eliminate this if in fact it's an issue in a aquarium.

Another way to keep this simple is just run high flow barebottom tanks.

 

[Doctorgori]

sea cucumbers are a must IMO with sand bottoms, although I now have a bare bottom and I actually saw my last one still alive (I have a pic somewhere)

I've seen several forum posts where sea cucumbers caused a tank crashed so I don't think that's the solution.

But UV lights should be a lot more effective in controlling bacterial density and a good substitution to cucumbers.

I have 3 UV lights, they have their caveats also: besides ongoing annual cost and maintenance they raise temps and require some automated shut off for flow failure …
Other thing mentioned is the emphasis on “substrate” pathogens….not sure UV addresses that

interesting article anyway, we have no clue how or what processes and interactions between organisms have importance