If you opt for cories, go for corydoras sterbai. They can take the same temperature as bettas, many cories cannot.
Personally, go for a sponge filter. Cheaper, but just as functional. Plus with a betta, the flow is gentle. A HOB may produce too much current for a betta.
All you will need is the sponge, an airline, and an air pump. Get a 20g pump or more, a 20g sponge or more.
Personally, go for a sponge filter. Cheaper, but just as functional. Plus with a betta, the flow is gentle. A HOB may produce too much current for a betta.
All you will need is the sponge, an airline, and an air pump. Get a 20g pump or more, a 20g sponge or more.