Thank you for contacting Polyform Products Company. Our clays do not contain any toxins, heavy metals or copper. While Sculpey is non-toxic, we have not done any testing on it in aquariums. I would recommend visiting message boards and forums to find out what others have experienced. I have not heard of any problems, but I am not involved in the aquarium community. There are some glazes that can be applied to Sculpey to make it water resistant, but as these glazes area made by different companies, I am not sure of their effect on fish. Sculpey can be placed in water without a glaze, but over time a whitish film may develop on the surface. This film can be wiped off with a cloth. I am sorry I do not have additional information for you.
If there is anything else I can help you with, please contact me again.
Regards,
