They are safe to use. Just make sure there is no glaze on them. Also, the hole on the bottom of them can prove to be a problem. Some bettas will try to squeeze through there. Unless it is a giant
hole, that's a problem. There are a few options for this...
- Saw out the entire bottom and make it into a tube. If you do this, SAND the edges so there are no jagged edges. Try putting a piece of pantyhose over it. If it snags, it is too sharp.
- Bury the hole part in your substrate so there is no possible way for your betta to try to squeeze through.
- Cover the hole or stuff it with something. I actually rolled up some aquarium safe netting and stuffed it in the hole nice and snugly.