I had to move Zen out of his 10 gal. into a 2 gal glass container while I put all the new plants in his tank and, actually, since his 10 gal. has rock gravel, I've not been able to see him have a bowel movement so now that's he's in the 2 gal container, he's staying until I see that everything comes out ok.* He's just a lil bloated, not badly.* Since Betta are so prone to constipation, I thought this was a good time to tend to that and to fast him a day or two or until I see he goes.
But, I have his 50 watt heater in the 2 gal. container with him.* Will this be ok

* Can it harm him in any way?
Thanks,
Karyn