How do they get ich? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 04-06-2012, 12:35 AM Thread Starter
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How do they get ich?

How do fish get ich? I added a fish on sunday but i am always really careful to look over the fish to make sure they have no signs of ich, I also ensure i never use any of the water from the bag when i add the fish. then yesterday, said fish and one other one dies, then i get home today, and 4 more fish die. how does this just happen???? This stinks!!!
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post #2 of 4 Old 04-06-2012, 01:20 AM
My understanding is that it's always there. Stress allows the parasite (which is what ich is) to take hold and multiply.
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post #3 of 4 Old 04-06-2012, 06:21 AM
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Ich can lay dormant for months, and as ladayen has said once a fishes immune system is compromised (usually by stress) it can take hold.

It's also not always possible to see Ich on the fish, it can be in their gills for example. A single parasite can multiply by the hundreds, so it only takes one.

However, I would not expect an outbreak of Ich to kill multiple fish in such short notice, the Ich would of had to of been really bad. This is a good reminder to everyone though how important quarantine is.
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post #4 of 4 Old 04-06-2012, 11:21 AM
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I agree with previous members. There is some debate among aquarists on ich, but there is sufficient evidence now to show that it can be "present" for months if not years without any visible signs. As soon as the fish are stressed by something, it will rapidly break out. This can happen in tanks with nothing new added for years, so clearly the ich has to be there. It is also generally present in all freshwater in nature, yet if you catch fish you won't see it.

An article in the current (April) issue of TFH by microbiologist Eric Hanneman describes this from his own experiences. He cured the tank of ich, and for several months the fish were fine. Then, suddenly in the winter the temperature in the tank dropped into the mid-60's F, and the fish were within a couple of days absolutely covered in ich.

I have had similar experiences with ich breaking out in tanks that have had nothing added for months. This is just one reason why preventing stress is so important. And stress can occur from many sources--inappropriate water parameters, sudden changes in parameters, ammonia or nitrite or high nitrate, too much light, inadequate environment, moving fish, using salt and chemicals, etc.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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