Regardless of whether or not you keep your betta in a community or a tank with live plants, it's crucial to choose a filter appropriate for the size of the aquarium. Bettas are carnivores - and they're not the cleanest eaters in the world. If you don't include a filter when you set up a betta tank, you'll quickly find yourself with a mess on your hand. Uneaten food will collect in the substrate, leading to a build-up of nitrogenous products in the water. And your fish will pay the price.