Typically "ich" refers to Cryptocaryon irritans, which is a protozoan; but there's also "black ich" which is Paravortex sp., which is a flatworm.
FW dips only work on "black ich" - the flatworms explode under osmotic pressure and fall off the fish. With the protozoans, there is the encysted stage, so while it looks like there may be no more infestation, they are still there. This is why a tank that's had an ich outbreak should stay fallow for a number of weeks - to allow the encysted tomonts to release infectious theronts, which without a host to attach to will die off, instead of repeating the cycle.
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-- Tony
My next hobby will be flooding my basement while repeatedly banging my head against a brick wall and tearing up $100 bills. Whee!
Last edited by Delphinus; 11-19-2007 at 08:29 PM.
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