All clay pots are not created equal. I know that some can contain lead and some do not. I was told not to use any for baking that are from Mexico and that the ones from Italy were safe. I was using a recipe to make that 'dirt' cake that was so popular with the kids years ago (made from cake and crushed oreo cookies lol). Anyways, if it is leaching out clay into the water the pot will probably disintegrate. Some of the clay pots can also have sand and stuff in the mix and then they definitely will eventually fall apart. Maybe you could pull out the pot and either re-seal it with something or just replace it with another pot.

Thanks for the reply. The pot is definitely history since the glaze/paint is completely peeled off. I scooped chips of paint out of the water, but the water itself is now the color of the clay underneath--- a terracotta color, so I'm assuming it's mostly clay. It was Talavera pottery from Mexico. Good point on food safety-- I hadn't thought of it that way. I'm sure it's not food safe since it was a pot meant for plants, not a bowl, so I guess I should probably assume that it's also not safe for the fish. I just hate to do a complete water change and upset the balance. Fish seem fine so far, but the water looks terrible (orange). Thanks again--- I appreciate your response! : )