Quick Cure is a mixture of Formalin and Malachite Green. So is Rid-Ich, and most other general 'turn your water blue' medications. You can buy pure malachite green in bulk in the pond section usually, as a koi remedy, for much cheaper. I have also read that Formalin and Malachite Green mixed togethor is very toxic, both to fish and parasites.
If I am not mistaken, both Formalin and Malachite Green will harm biological filtration..