Well according to my ---- Mills Marine Aquaruim book page 56 under basic health care he says (this is what I recalled when posting) " The quarantine tank can also double as a treatment tank. Apart from a few flowerpots and slates against the walls to provide refuge it will need little in the way of decorations. Besides heating 2 other life-support systems are necessary; aeration, and a suitable but simple filtration medium, since activated carbon and other chemical active media may remove medications from the water". I have a couple of clay pots that I have used for larger fish in recovery and have never had a problem that I can say was from them. There is even a picture on that page of a tank with 2 flowerpots in it.