You could also get some snails. I had a mystery snail with my betta but it was too messy for the small 2.5 gallon tank. I was surprised by how active they were, and the betta never really bothered it other than a little bit of posturing. Your betta should LOVE plants. The behavior of mine completely changed once I put live plants in his tank and he loves swimming through them and lounging in them. He also started building a bubble nest which is fun to watch. I have Crypt wendtii and Crypt spiralis with mine, and Bettas are supposed to really like the Anubias family of plants which you train to root on a rock or piece of driftwood.
