Are any fish naturally immune to MI?

[Brett S]

Hello all,

My first post is a question and a confession.

I have a 100g system that is about 3 months old. I succomed to the pressure of my wife proding me to skip the quarantine process on the Coral Beauty we bought about a week and a half ago and just dropped him straight into the DT since we had company coming in from out of town. (I know, I am a grown man and perfectly capable of making decisions for myself) I am now the not-so-proud owner of an MI infested aquarium.

After reading a ton of information on this nasty problem, I know what I need to do to cure my problem, but I dread it. I've already got my QT set up (I actually had it all set up prior to the infected new addition), and I've caught all the fish except the last three. These guys are much faster than I am and don't fall for any fish trap I've built and tried so far, but maybe they just aren't hungry enough. So far I do not see spots on these fish, but I figure it is reasonable to assume they have the bug.

My questions are:

• Are any particular species of fish more or less prone to immunity of MI, and if so, must they be removed anyway in order for the aquarium to be "fallow"?
• While the tank is "fallow" how do you keep the benificial bacteria alive? I assume no fish = no poop, which = bacteria starve and die. Is this true or false?

I'm afraid I know the answer to the first set of questions, and this is going to mean my Blenny must be removed which I am sure is going to cause me to take my entire rock pile down. The thought of going through that again is not a pleasant one as it still doesn't look right after the last time I did it. Just FYI, it is all dead rock, but there is a ton of it.

I know i could try the hyposalinity cure, but I do not trust my ability to control the water quality in a 100g system given my travel schedule and just being crazy busy.

I have learned my lesson early about the benefits of the quarantine process and I will not make this mistake again.

[FoMoCo Master Tech]

Sorry to hear about your situation Brett. Sometimes, the lessons that hit home the hardest are the ones learned through experience.
There are fish that have a higher resistance to MI but I don't thing there are any totally immune. I would think if it's got gills, it can be infected. Your other fish may not show signs of ich and may not die from it but as long as they are your DT, your tank will not be free from the parasite. As you know, MI cannot live long without a host fish. Once MI is introduced, the DT has to go through a fallow period (8 weeks or longer) to allow for the parasite to go through it's life cycle and die.
I can understand the difficulties of catching all the fish but it has to be done in order to rid your tank and fish of MI.

While the tank is fallow, feeding it a small amount of food every couple/ few days will make sure the bacteria and clean up crew have something to eat. The bacteria population will change without fish so you'll have to reintroduce the fish slowly to allow the bacteria population to adjust to the new Bio load (1 fish every couple/ few weeks).

[leebca]

Marine fishes have an immune system between that of mammals and that of invertebrates. Not very good. When they do gain immunity, it only lasts a few months.

Fish do sometimes gain such a temporary immunity, but not the kind of immunity you are generally familiar with. Their immunity is more of the innate kind, rather than a specific kind. Specific or learned immune responses are not that common, but when forced, like in giving the fish injections, can last 2-3 years. But that is as long as it will sustain itself.

To put the above in perspective. Wild fishes have been found to be infected with Marine Ich in up to 30% of the population, in certain areas. In the wild, they don't develop an immunity. The captive fish faces a different set of circumstances -- the fish can't get away from the multiplying parasites like they can in the open ocean and seas.