Join Date: Jul 2013
Location: Gainesville, FL
Well, yes and no. In such a small tank I would not recommend relying on plants alone for filtration unless you are really aware of what you are doing (some may disagree). But they can help!
There are a lot of smaller, easy plants to choose from...java fern, java moss, Anubias spp. smaller Cryptocorynes are just a few. Hornwort is good as it sucks up nutrient quickly, however I've had bad luck with it myself. What is the lighting situation like? A lot of these will do ok without much, but they do need some light.
Is this tank filtered? Do you have a good, liquid test kit? The latter is essential to make sure that your ammonia (and also nitrite!) are monitored. Then lots of water changes will make sure they stay very low and do not effect the betta as much as possible. Again, water changes will go a long way!