RE: Ich
It really depends on what you define as "ich" as to whether it is always present.my understanding about ich in freshwater is it is ALWAYS in the water and you cant really do anything about it aside from keeping pristine water.
not sure if the same applies to salt, but im sure it does since we get our water from the ocean in one way or the other
Freshwater ick is short for parasite Ichthyophthirius multifilis (ich because nobody can pronounce that name). This parasite is not always present and can be erradicated entirely but their is another freshwater parasite called tetraheyma which is pretty much always present and takes advantage of the fish when it is stressed. Tetrahyema looks identical to ich unless you look at it under a microscope. If you ever had freshwater ick that was REALLY hard to get rid of and took out fish very quickly...that was probably tetrahyema.
Saltwater ick is generally defined as the parasite cryptocaryon irritans. It is not always present and can be completely erradicated with the proper use of copper, which is the only 100% effective treatment I know of. It is the marine counterpart to freshwater ick but is 100% unrelated to it and is a good example of concurrent evolution in that it looks like freshwater ick and also has almost the exact same life cycle as freshwater ick. There are several protozoans that are analogous to freshwater tetrahyema that are probably always present and produce the ick like symptoms when the fish are stressed.
Keep in mind that these are microscopic parasites so when you are looking at white spots on a fish you are not looking at the actual parasite. Instead you are seeing the fishes immune response to the parasite which is mucus production around the parasite which is embedded in the skin of the fish. This is why you might here someone say they did a fw dip and the ick was all gone but then returned the next day or two because the fw washed away the mucus making the white spots but not the actual parasite.
This is why there will always be the debate of wether ich is always present or not. People just are not necessarily talking about the same parasite. So to me it's not worth getting involved in such arguments. Also the reality is that most of us (myslef included) do not follow strict enough quarantine and often introduce cryptocaryon into our display tanks and so it will always remain in the system unless the system is kept fallow for a minimum of 4-6 weeks. In this case, we have to rely on the fishes immune system to overcome cryptocaryon which involves keeping the water quality high and feeding the fish well. It also helps NOT to introduce too many fish at one time since fish are never completley immune to cyrtocaryon. So introducing too many new fish may provide enough of a vector to overwhelm the fish that were able to resist the parasite.
Quarantining to give 100% guarantee that cryptocaryon is not present is quite difficult. You would have to qt EVERY fish under copper treatment for at least four weeks since copper only kills crypocaryon in it's free swimming stage. Hyposalinity is usually very effective but not 100% of the time. You would also have to qt every piece of coral and liverock since it is possible to bring in cryptocaryon on those too. Not real likely but possible.
Here at the store we do a brief qt on susceptible fish, use hypo and copper as needed, to reduce the odds of sending cryptocaryon and other parasites home with the fish but we can't offer a guarantee on that. Most people aren't willing to pay for that level of qt and even if they were, I'm not sure it can be done at the retail level. Probably something that has to be done at the hobbyist level.
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Originally Posted by Richard
