taracotta as in:
-a pot i just bought in a store
or
-some clay i jsut made labeled as teracotta
or
-unknown pot made of "teracotta"
??
in general, most people can use clay pots in their aquariums, but remember that since clay is extremely porous, it may very well have some nasty solutions that you dont want in your tank if it is not new.
but again, always check labels and history, etc;
Good Luck,
Black_Wolf