I had to move my mandarin to my display early for this very reason. I have heard that they are a little less susceptible to ich but I don't know if I believe it
Mine was in QT
for 2 weeks when I noticed his belly shrinking. He is fatter than ever in my display.
The filter idea is a good one. I keep a filter in my fuge in case I need to collect any pods
. I had a tank that I thought did not have any pods
until I cleaned the prefilter on one of the PH