"Okay" is not thriving, there is a major difference between care that barely scrapes by and following the recommended guidelines. You need to do a little more research on proper care. Betta splendens are a species from Thailand (formerly known as Siam). Much of the country is classified as being...
You need to edit your post to include that an aquarium heater is a MUST for Betta splendens in a temperate environment. They are a tropical fish and require a water temperature between 75-82 degrees Fahrenheit in order to be healthy. A thermometer is needed to ensure the temperature is stable...