11-28-2009, 06:53 PM
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Correct NC Frank. Ich is a parasite, but is present in most aquariums. A healthy, unstressed fish is able to fight off infestation issues. A stressed or unhealthy fish becomes vulnerable because it is not naturally able to fight it.
When we bring a fish home from a lfs many of them are carrying the ich parasite, we just can't see it because it is microscopic and it can be present in the intestinal tract and in the gills either in protozoan form or as a cyst. These things are not seen by the naked eye when we look at the fish, and unless the immune system of the fish has been weakened from things such as dirty water, stress, other illness, etc. this fish can carry the parasite into a healthy tank where the cyst will drop into the substrate unseen and begin to reproduce.
When we see the white dots on the fish, the white dots themselves are not just the parasite. The white dots are the fish's slime coat over the parasite, as the fish is trying to naturally fight off the parasitic infestation.
Sorry ghreed... your info is not completely accurate. The dirty water, pH shifts, etc that you accuse other of "blaming" the infestation on, are indeed what bring on the infestation due to the fish's weakened immune system that these things cause, and their inability to fight it naturally. Most fish will carry the ich parasite even though we can't see it. It is the conditions listed that cause the problems.
A tank that has been healthy and "ich free" for years with no new fish additions can indeed suddenly show up with a problem with ich. The reason for this is because the parasite is already there, but conditions change which makes the fish vulnerable to it.... such as the case of frequent/rapid temp fluctuations, dirty water, etc.
I hope this helps to clarify.