[bigbadjon]

I would suggest plastic. Why would you put anything in a quarantine tank that you can't sterilize and may harbor pests?

 

[Nordic]

You need to treat everything that comes close to your hospital tank like it is contaminated.
So, you want stuff you can sterilize occasionally.

 

[nel]

Or just throw it away. Java Moss will be good. Just set a jar, or whatever else you want, with it and add some part of it to the quarantine tank. After treatment/quarantine throw it away.