Ich discussion again

[JohnnyRedd]

I asked this before and there was some dialog but apparently thread life is very short here as there is nothing older than yesterday.

A tank comes down with ich. Whatever fish die and whatever fish live. No more fish are added.

What happens to the ich? It's present for at least a cycle but does it die off once the fish develop an assumed immunity to it?

It's kind of a side bar to allowing a tank to remain fallow for an extended period - what is happening in a tank with fish that are not showing signs of ich anymore for 30-60 days?

Everything I read on ich is about the now and the fallow treatment of the tank. Struck me the other day after reading a FB post about a tank that had previously had ich and he was wanting to add more fish - like 6 months later.

Thanks

 

[Breakthecycle2]

No, it takes years for a strain of ICH to eventually die off. Leaving fish in your tank that have immunity will not do anything to stop the cycle. Technically speaking, the parasite is still feeding off the fish.

 

[scooter31707]

if the fish live and it does not show, the fish can become immune to it, but ich will still be in your tank. The only way to rid the ich in the tank is to take the fish out and let the tank go 72 days fallow. Some hobbyist have gone 90 days to be safe. Once you add a fish they then become infected and any stress can result of the old fish getting it again. Maybe the experts will chime in soon.

 

[Dealseer]

Deja vu.

 

[Jeff4777]

For complete irradication, all fish must be removed and go fallow for a minimum of 72 days. Even if the fish currently in the tank exhibit no symptoms of the parasite. Those fish will also need to be treated, preferably with TTM followed by an observation in a sterile QT.

 

[ThRoewer]

Full immunity does not just prevent a fish from getting sick, but also kills every ich parasite that tries to settle on that fish.

So if the fish are fully immune the ich in the tank will die out rather quickly. But if even one fish is only partially immune, the cycle will continue, just on a lower level.

The issue is that you may only know in hindsight if the fish you left behind were fully or just partially immune. That's why this is a rather risky approach.

It worked for me once with fish I knew to be fully immune due to their history. It wasn't even planned that way, I just didn't have the space to treat all fish of that tank at once and so just treated the fish in need while leaving the ones that weren't in need behind. No new fish added to that tank ever showed the slightest symptoms. And that is my over crowded tank with a rather high stress level.

There is also species difference in the ability to acquire full immunity.
I found that some fish seem to have a natural resistance/immunity to ich while others may acquire partial, but rarely ever full immunity.

So, if you want to be sure that all ich is out of the tank you better take the fallow approach - for 3 full months and not just the 72 days many incorrectly claim to be the required time.

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[Breakthecycle2]

Full immunity does not just prevent a fish from getting sick, but also kills every ich parasite that tries to settle on that fish.

So if the fish are fully immune the ich in the tank will die out rather quickly. But if even one fish is only partially immune, the cycle will continue, just on a lower level.

The issue is that you may only know in hindsight if the fish you left behind were fully or just partially immune. That's why this is a rather risky approach.

It worked for me once with fish I knew to be fully immune due to their history. It wasn't even planned that way, I just didn't have the space to treat all fish of that tank at once and so just treated the fish in need while leaving the ones that weren't in need behind. No new fish added to that tank ever showed the slightest symptoms. And that is my over crowded tank with a rather high stress level.

There is also species difference in the ability to acquire full immunity.
I found that some fish seem to have a natural resistance/immunity to ich while others may acquire partial, but rarely ever full immunity.

So, if you want to be sure that all ich is out of the tank you better take the fallow approach - for 3 full months and not just the 72 days many incorrectly claim to be the required time.

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Why is the 72 days incorrect?

 

[ThRoewer]

Why is the 72 days incorrect?

If you take the last fish out a protomont could have just left it. This protomont has 18 h to encyst. That pretty much adds already a day.

Then the tomont (cysts) may last the observed 72 days.

Should it hatch right on the 72 day mark the hatched tomites can live for another 48 h.
And while they are usually only infective for the first 24 h it is safer to calculate the full life time.

So 1 + 72 + 2 gives a total of 75 days.

If you then take into account that the 72 day encysted period is based on a single observation, it's rather reckless to take that as a hard number.
It is rather just a clue that ich cysts can last for quite a while under certain conditions.

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[Madmax412]

Does tank size have anything to do with the lifespan?


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[Tripod1404]

In a closed system with no outside introduction of new strains, Ich will slowly lose its genetic diversity. All while available host within that closed system will become harder to infect due to immunity. So ich will eventually be out competed by the fish. The issue is time it takes for this to happen. It can take years for the strain in your tank to become "inbreed". The simpler the organisms, longer it takes for it to lose genetic diversity. Ich is a Protozoa so it is far mor complex than say a bacteria, but also far more simple than an animal or plant. So while an animal can becomes inbreed pretty fast, ich can remain infectious for a long time.

 

[ThRoewer]

Another thing that has to be considered is, that ich as protozoan is on many inverts menu. Filter feeders and corals are the primary enemies of the free stages, while shrimp and copepods may go after the ripe protomonts before they can encyst.
While this may never be enough to wipe ich out directly, it definitely can keep the numbers in check.

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[Tripod1404]

Another thing that has to be considered is, that ich as protozoan is on many inverts menu. Filter feeders and corals are the primary enemies of the free stages, while shrimp and copepods may go after the ripe protomonts before they can encyst.
While this may never be enough to wipe ich out directly, it definitely can keep the numbers in check.

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Yep, even other bigger meaner protozoa would go after ich in its free swimming stage. I would assume any predatory protozoa, such as amobeas, would eat ich. This is one of the arguments against using UV sterilizers for ich. Basically UV kills everything in water column. Only a fraction of ichs life stage takes place in water column but many of its protozoan predators might be largely pelagic. So a UV kills far more of them than it kills ich.