Will I Need to go Fallow?

76fishman · Apr 25, 2018

My blue hippo tang recently contracted ich and popeye and I had 2 juvenile emperors die for reasons still unknown to me (not ich, velvet or flukes).

My blue tang and perc are the only fish in my larger tank and show no signs of parasites or sickness.

Currently in the process of upgrading tanks so the only livestock which will be added to the larger tank will be from the smaller tank.

All fish in the smaller tank have not shown any signs of sickness for the entire duration the tank has been running.

Is it safe to assume the fish from both tanks have built up a strong mucous layer to be “immune” (parasites can not penetrate) to these parasites?
If they have built an “immunity” will the parasites die off, since they can no longer host?
Do these parasites lie dormant within the fish after one contraction of a parasite?

DLHDesign · Apr 25, 2018

76fishman said:
Is it safe to assume the fish from both tanks have built up a strong mucous layer to be “immune” (parasites can not penetrate) to these parasites?

No; that is not safe to assume.
The "immunity" of your fish is really more about the health of your tank; not anything different about the fish in the tank. As a healthy person is more likely to fight off disease (the cold, say), so to are healthy fish able to better fight off parasites and disease. But should the same person suffer from poor health (being overly tired, dehydrated, lower body temperature etc.), their body becomes more susceptible to the disease and they have a higher chance of catching the cold. The same is true of the fish. So long as they are (relatively) free of stress, have a good supply of food, and are kept in a clean environment - they can continue to fight off the majority of the parasites that may find their way onto them. This keeps the parasite population low (to the point of usually not even being noticeable), but it does not guarantee that the state will remain that way.

76fishman said:
If they have built an “immunity” will the parasites die off, since they can no longer host?

Yes and no. A given parasite may die off, but the infestation will not. This is due to the lifecycle of these things; the "attached to fish" stage is only one of several stages of the life of the parasite, so even if all your fish are clean at the same moment, the tank itself still houses the parasite in some stage. You would have to be crazy lucky to have all the parasites die off in an infected tank without intervention.

76fishman said:
Do these parasites lie dormant within the fish after one contraction of a parasite?

Not "within the fish", no. But "within the tank", yes. See here for more info on ich.

In short; if you want to get ich-free; yes - you would need to go fallow for 76 days while your fish are treated in a QT that is at least 10ft away from your display tank(s). It's either that, or you can look into "managing ich" options.

deedubz · Apr 25, 2018

Short answer, no.

Without knowing what killed your angels, and without a pic to confirm it was ich on the tang, there's no easy way to answer your question. Something killed your fish. Some parasite was on your tang. Your surviving fish will need to go into qt to be treated. The fish in the smaller tank will likely need to be treated as well, unless you're 100% certain you've never cross contaminated the tanks (equipment sharing, not washing hands, heck even washing hands and putting them in the the other tank soon afterwards). You'll also want to go fallow after the transfer.

My recommendation would be to treat all your fish now before placing them in the new tank. It'd be a shame to have to break it right down to catch everyone for treatment. I'd do 30 days copper followed by a couple rounds of prazipro in qt

deedubz · Apr 25, 2018

Here's a thread about eradication vs management
https://www.reef2reef.com/threads/ich-eradication-vs-ich-management.188775/

76fishman · Apr 25, 2018

Do you mind explaining why the tanks must be 10ft away from each other? I assume it has to do with cross contamination.

So, by all this logic, a tank can never be fully free of parasites, even with the tank going fallow and any and all fish being placed in a QT?

DLHDesign · Apr 25, 2018

76fishman said:
Do you mind explaining why the tanks must be 10ft away from each other? I assume it has to do with cross contamination.

Your assumption is correct. It's been found (via scientific study) that it's possible for parasites in certain stages to be involved in aerosol transmission up to 10ft away. That is; a very small bit of water containing the free-swimming parasite is ejected from the infected tank and "splashes" (though perhaps "floats" is a better word) away from the tank - potentially landing in another tank and being introduced there.

76fishman said:
So, by all this logic, a tank can never be fully free of parasites, even with the tank going fallow and any and all fish vein QT’d?

Not true; no. If an established tank is kept fallow (fish-less) for 76 days, only properly QT'ed fish, inverts, and corals* are added into it, and proper precautions are taken to prevent cross-contamination, then the resulting tank would be free of the parasites that have been treated for.

* - Inverts (snails, etc. - anything "non fish") and coral would be QT'ed against fish disease by placing them into a properly located QT tank for 76 days before they are placed into the DT. Some coral providers keep their stock in fish-less systems already, so this isn't always needed if you know that to be true. It's always a wide precaution anyways, as you'll want to ensure that they aren't carrying any other pests into your DT (which is why "dipping" corals is still part of the process - but that's not for the fish per-se...).

HotRocks · Apr 25, 2018

76fishman said:
Do you mind explaining why the tanks must be 10ft away from each other? I assume it has to do with cross contamination.

So, by all this logic, a tank can never be fully free of parasites, even with the tank going fallow and any and all fish being placed in a QT?