Betta fish are often housed in bowls. That means no filter, and no heater. Even people who keep Betta fish in small tanks rarely provide filtration or heated water, and they survive for the most part.
Really, this is what makes the Betta so popular. For beginning fish keepers, kids, college students and others who don't feel like dealing with the maintenance requirements of a real aquarium, the Betta is a way to have a pet fish without all the hassles of having a pet fish.
Unfortunately, these same Betta owners later end up wondering why their fish appears perpetually stressed, or suffers from some malady such as fin rot. Betta may survive in bowls of stagnant water, but that doesn't mean they are thriving.
Cold temperatures and dirty water can cause stress for your Betta and make him more likely to get sick and die before his time. But this doesn't mean you can't keep your Betta in an unfiltered, unheated tank. It just means you need to fully understand the requirements of your Betta fish before deciding if that is the correct decision. It also means you need to be ready to do the extra work required to keep an unheated, unfiltered setup in top condition for your fish.
In this article we'll take a look at whether or not you should consider housing your Betta in a tank with a heater and filter. If you are new to Betta keeping, you might want to first check out my article on proper Betta care:
How is the Betta Different from Other Fish?
What makes us think it's okay to keep a Betta in a bowl, anyway? We'd never consider putting any other tropical fish in a tiny bowl without a filter.
Betta fish do have physiologies that allow them to survive in low-oxygen environments in the wild. They are anabantids, or labyrinth fish, and they can come to the surface to take a gulp of air when they need it.
By the way, this is just one more reason keeping a Betta in a plant vase is a really stupid idea. Your Betta fish needs access to the water surface!
In the wilds of Southeast Asia Betta can live for short periods in small puddles where other fish would perish. This is because of evolutionary adaptations that allow the species to persevere in times of drought or poor water conditions.
In other words, they have evolved to take in air, not just rely on the oxygen in the water, so they can survive harsh conditions.
This makes them the perfect fish to house in a small bowl, or so it seems. They can do without the aeration effect of a filter, and survive even if the water gets dirty.