Clay DIY Aquarium rocks

Question
Hi, Corrina-
Have you ever heard of someone making their own rocks, caves, etc. out of Polymer clay?  I can find plenty of questions, but no one seems to know for sure if anyone has ever killed their fish w/this medium.
I klnow earthen clay can be used, but I'm very wary of glazes, since many contain metals.
Polymer clay comes in all sorts of colors, and can be fired in the oven, but this sounds too good to be true.
I really want to customize Cichlid caves....
Thanks-

Answer
Wow I haven't heard of anyone makeing there own rocks or anything like that.If you really want to do this then do a test first. Put your rocks or caves in to a small tank and see if it changes the water color, temperature, amounia ...etc. If you can't find anything different buy a feeder goldfish (a really small generic goldfish) and if they survive after a while i'm pretty sure your good to go. but i must warn you that some goldfish could survive anything and some are very sensitive so this experiment could still go astray.
corinna