I've used several pots other than terra cotta with no problems. I have some ceramic pots that are glazed and sealed that are in a 20 with an african frog right now--they are lovely, and protect the plants from the frog. He's grown about an inch in the monthes I've had him in there, so I assume the setup works for him as well.
What I recommend is soaking the pot in a white bucket for a few days. If the water doesn't change color, and the pot doesn't change composition (no mushy spots, nothing flaking off, ect) than I think you're safe. If it's not a brand new pot, I'd worry about ferts and pesticides that might have been used and absorbed by the pot.