Would you treat a fish that seems to have recovered from ich?

[Dag]

For the first three days after I got my powder brown tang (acanthurus japonicus) it had ich and I kept it in the QT. I was about the to start hyposalinity and the ich seemed to disappear, so I did nothing and the ich has not been visible for three days thereafter. I was going to continue doing nothing and just observe him for another two weeks or so.

He seems to be very alert now and he is swimming into the current coming from the powerhead. I'm concerned that his swimming into the current from the powerhead is somehow a sign that he is still bothered by parasites not visible to the eye.

I would like to wait and see, since noninterference is my preferred mode. I posed the question to ATJ in the fish disease forum, and he seemed adamant that I should have immediately started hyposalinity and should apparently start now. Here's his conclusion:

It seems pointless to quarantine the fish if you aren't going to treat it now you know it is infected. One of the main reasons for quarantining fish is to avoid the introduction of diseases or parasites into you main tank. You know your fish is infected and if you don't treat it, you can't be sure it is no longer infected.


Can I get a second opinion on this?

[Steven Pro]

Sure, I would use hyposalinity with an accurate floating glass hydrometer or refractometer.

Quarantine is great. And, in this case has saved you from infecting your entire tank, but this fish could still be harboring lethal levels of the parasite in the gills. Plus, just because the spots appear and disappear over a few days only means that the disease is reproducing and progressing just as it is supposed to do. They only stay attached to the fish for a few days. Then drop of to reproduce. The thing is when they reappear, it is usually many times more the original infection level. Treatment at that point maybe too late. It is better to nip this in the butt now.

[Dag]

I was employing one of the methods you suggested, frequent water changes. Isn't it possible or perhaps probable that I broke the cycle by siphoning out the cysts, or through the natural defenses of the fish?

I guess you're thinking hyposalinity is not a big risk to the fish, so why not?

[Steven Pro]

It is possible to effect a cure with daily water changes, but you must be very diligent. A 50% water change once per day, everyday for two weeks. Otherwise, there are no gaurantees.

There is no risk with hyposalinity if you have an accurate means of measuring the salinity. I would not recommend using hyposalinity to anyone with only a cheap, box-style hydrometer, though.

[Dag]

I have a refractometer.

Would you also recommend frequent water changes of the QT during the hyposalinity process. I was thinking 20% every three days.

[Steven Pro]

I also wanted to add that one must be keep a close eye with hyposalinity, too. Evaporation could quickly elevate the salinity in a small QT tank high enough to make the treatment ineffective.

[Steven Pro]

Originally posted by Dag
Would you also recommend frequent water changes of the QT during the hyposalinity process. I was thinking 20% every three days.

There is no real need for it, unless you are having some osrt of trouble maintaining appropriate water quality such as ammonia or nitrite. Also, monitor your pH. Some people have had problems getting a good pH level because of the lowered salinity level. You will probably just have to use a little buffer.