You do not need a filter system, no, as your entire tank or bowl provides a biological filter. That is the type of filter that removes ammonia. Beneficial bacteria grow on all surfaces, the gravel, decor, etc. It will not grow as readily on glass, though, so if your substrate is glass rocks or marble, you might want to change that out. Also, if the betta is in a small bowl, please provide a more appropriate home as they get quite large, require 2-5 gallons minimum, and a heater. They do not have to have a filter, although they do prefer clean water, so without a filter, be sure to change some water every day.
Date published: 2018-03-15