I was trying to encourage my betta to make a bubblenest, however he's taken to liking this little toy as just a hang out spot. I took a plastic cup and cut it to about 1cm, and I let it float at the top. There's an air supply under there and he seems to like it a lot!
The only issue I see is that toxic gasses MIGHT build up under it, poisoning his air supply. I don't know if he would notice it and go to the rest of the area, or if he would just begin to poison himself.
If there IS some sort of gas release from the biochemical reactions going on in his tank, would it harm him?