Parasites

[billwarren]

Is it possible for a fish to get parasites when they are stressed and then lose the parasites when they are put into a calmer environment?
A lot of my fish are getting parasites and I believe it is stress being caused by a Rabbit fish and a sailfin tang that are reaking havock in the tank.
The sailfin and rabbit pick on other fish and have been responsible for a few of them dying from stress.
Bill

[leebca]

Bill,

You've asked a question which is fundamental to our hobby. It is controversial and raises the emotional level in many hobbyists. I don't think there is any doubt in my mind that obligate parasites don't need a means to attach an available host fish. Fish that are sick or healthy, stressed or secure, are susceptible to obligate parasites.

How well the fish's immune system and defenses hold up when they are stressed is another topic. I believe these two things are depressed during stressful situations. For those parasites that can't get to the fish unless their defenses are down, it is an opportunity for them to move in. But, I am not writing about obligate parasites in this case.

A weak parasitic attack can create a temporary immunity in the fish, to the parasite.

But let's look at some facts in your case first:

List all specimens (fish, inverts, corals, clams, etc., etc.).
Do you use a quarantine tank and procedure?
Foods you use and feeding schedules.
How long have you had these specimens?
Do you use any vitamins? any additives? Please list all.
Chemistries (Ammonia, Nitrite, Nitrate, Phosphate, Silica, Ca, Alk., and any others you have)
Water parameters (pH and your pH range, salinity or sp. gr. & range, temperature range)
List what you added or taken out of your aquarium system (living, decorations, and equipment) during the past 4 weeks.

When it comes to obligate parasites, the primary infection event is that a fish brought it in with it.