[Rosscopeco]

That's a pretty quick turn around for ich. One day doesn't seem long enough to cause death.
Velvet on the other hand will act that quickly.
Read through the article linked at the start of this thread for solid info on how to handle ich. Most of the otheir info in this thread is not worth a pinch.

My experience with ich has been text book and everything in that first article rings true. Unfortunately, ich found a gap in my original quarantine procedures and all hell broke loose after the tank was well established.
If your tank isn't too old it's worth doing everything in your power to get those fish out and start a new quarantine regime. You'll be happier in the long term if you can keep ich out of the tank all together.
On the other hand, if you're like me and can't get all the fish out without killing them in the process, you will just have to cross your fingers and hope for the best.
I have a four year old reef that was heavily stocked with fish and corals which made it impossible to get all the fish out of. After losing half my fish stock over a week to velvet and ich I tried everything to get the fish out for treatment. Even with all the water removed and the rock work high and dry some fish were inside the rock itself. Short of killing them i eventually gave up.
Given the choice I'd always opt for treatment and quarrantine.

A year later and the tank is healthy with no more outbreaks or stock losses. I consider myself lucky to have got off so lightly.