I have big problems with a sort of Ich after i put yoyo loaches in my main tank 800 L ( even after quarantining them for 3 weeks !)

All my big clown loaches are still covered with Ich after a week treatment with Esha Exit in combination with Esha 2000 ( Always made good experience in the past with this combination. I also raised the temperature and put in some strong aeration as well. But so far no real good results.
So this morning i went too my local fisch store and asked them what to do.
They told me to use Sera Protazol

I hope they will recover they took such long time in growing big.
Thanks
Patrick