Any updates on the fish? Hope your treatment brought him around.
this is what I used on my prefilter.
https://www.servapure.com/assets/ima...-specsheet.pdf
it is rated to be able to take care of the chlorine at the rate I'm running it.
I do add prime as well (but I have skipped a few time I have to say).
I'll take a closer look if there is residual chlorine or not.
FrancK
2018 year of the big tank!!!.