Alitheia~ I don't like plastic plants much for just that reason; they are much too hard and sharp for delicate fins... I know a lot of folks prefer them, but not me. For each of my bettas, I have a live plant (an amazon sword) and a small hiding place in their bowls, so that they don't feel so out in the open. It's done wonders as far as torn fins and such, and contrary to what some think, it's no more work to tend to a live plant. Just make sure you get a sturdy plant, and that the bowl gets plenty of light during the day (though no direct sunlight, freaks out the fish). When you pick out something for them to hide in, make sure to check for sharp, rough edges, as you could run into the same problem again. Especially with those bettas sporting long, flowing fins, those tears can happen just swimming against something rough.
Keep giving him bettafix, sea-salt his water a little bit, keep it clean (dirty water is supposedly the biggest cause of fin rot), and cross your fingers that he doesn't throw a tantrum and tear himself again! Good luck!
Stupid plastic plants!
