Are plastic boxes safe as quarantine tanks? and Ich questions

[CarpCharacin]

I never had a cooler leak. If they have the lids it keeps the fish calmer and temps even. The fish I have currently were transported in thick styrofoam with no issues.

lol, whut? styrofoam cups...

Styrofoam isn't entirely waterproof, even though it is a closed cell foam, there are interstitial gaps between the individual pellets that create channels between the pellets.