OK folks, ICH can't come from temp being off, salinity being low, sand being stirred, nitrite being high, or whatever. All of these things can weaken a fishes immunity to ich, but don't cause it. A person can be low on vitamin c, go play out in the rain and not get any sleep at night, but they're still not gonna catch the flu if they are not exposed to the germ.
HTH,
Mariner