quaranting

Question
I have been isolating sick fish for the past  few years but all
of the fish isolated would die the next day....there usually
only one fish isolated at one time in a carry on tank
everytime and i would decorate it with some rocks and a
bit of gravel.and a airstone but it would still die the next
day...wat should i do?

Answer
Hi Elizabeth,
Are you providing a large enough container for the isolated fish?  Toxin build-up can the fish especially because the isolated tank has no beneficial bacteria to break down the nitrogen.  

Also, did you de-chlorinate the water before adding?

Sick fish need pristine water to encourage health regeneration.  Water quality is very important because it relieves stress on a fish.  If all the fish haven been dieing the next day, then I would think water quality is the culprit.

Do water changes more often in the quarantine tank and replace with DE-chlorinated water.
-Matt-