where does ich come from?

[smokey11]

My fishes got ich today after I did a 1/2 water change ysday. It got me thinking, where did the parasitic disease come from?

The aquarium is a relatively closed ecosystem, the only exposure to external environment is when I change water. So does that mean our common tab water have parasites like ich?!

[ezy33]

It was explained to me by a LFS owner. Ich is like the common cold, it's always around and stress will weaken the fishes immune system. I've good luck using garlic extract ( I like Kent's Garlic Extreem ) to boost the immune system.

IME the max water change should no more than 10 to 25% under normal conditions.

[absolutangel04]

I disagree. Going on all the things I have read, ich is not always present in every system. Many people believe that because of how it pops up, but ich is not in all fish tank water all the time. I have heard people say that same thing about ich being in all tanks, but from what I have researched about the nature of the the ich organisms, that is not true.
Ich generally comes in on new fish. Often, it infects the gills first so fish can be carrying it, but you won't see it. It is true that once a fish's immune system lowers they are more susceptible to getting an ich infestation, but healthy fish can get it too if the ich is prevalent enough.