Best Betta Fish Filters; The AAP Sponge Filter

Many affiliate blogs will promote HOB or Internal Filters as the optimum choice for a Betta Fish Filter.
HOWEVER, the truly best filter for a Betta fish based on real world experience such as that of Aquarium keeping expert and author Carl Strohmeyer, is the Sponge Filter.

Even then, among sponge filters the USA made AAP Hydro Sponge should be your first choice.
As for type, the fine generally is your best choice since it will trap finer debris and has a slightly higher bio load capacity.
This said, if you want the optimum sponge filter, a combo fine/coarse would be your best choice, such as pictured below [1/3 PRO Combo from AAP].
Beware of social media sellers that promote ONLY coarse Chinese made sponge filters, which have their place but certainly are not the best choice for a Betta fish.

WHY THE SPONGE FILTER?

Sponger Filters are much less likely to cause damage to delicate Betta Fins, especially the tail fin.
Despite the popular social media myth about stress induced Betta tail biting that is further perpetuated by search engines [especially Bing's highly inaccurate Bing AI], damage caused by filter intakes is one of the leading cause of betta tail damage according to experts over the decades.

A little more about this myth, especially since it has picked up steam of late;
Stress induced betta tail biting has been considered and proven a myth for decades.
To date, no video evidence has been presented to prove this myth is actually true, as all videos that show a betta biting itself are clearly acts of aggression, generally from reflections of the same betta in the aquarium/bowl glass.
MOREOVER, science dictates that it is the person who is trying to disprove established science to present evidence that their theory is the correct one. NOT THE OTHERWAY AROUND as many now would have you believe, even search engines such as Bing [whom now censors many science based aquarium keeping websites so as to present the false truth they want you to believe]. And as noted, the decades long established science has been that betta fish do not bite their tails due to stress like a dog or bird might do.

BACK TO THE SUBJECT AT HAND, sponge filters for betta fish; these filters are among the best bio filters for their size and also they do not attract Aeromonas bacteria like some filters can. Which, Aeromonas bacteria infections are among the other leading causes fo betta fin damage and even death.

Sponge filters also work well in bare bottom aquariums which can help with ease of cleaning and lowing the amount of mulm in an aquarium [which can also attract Aeromonas bacteria].

So in summary, in most instances, your best choice for a betta fish filter is a sponge filter [fine or combo]. And why not buy from the decades long leader in aquarium keeping information; AAP, rather than the many lower quality knock offs from China now flooding the market?

Resource for the best USA made Sponge Filters;
AAP Hydro sponge Filters

Further Reading as per expanding upon information provided in this short article:
*Stress Induced Betta Fish Tail Biting; Myth or Fact
*The Myth of Stress Induced Betta Tail Biting; From Fish as Pets
*Fish Aeromonas & Vibrio Disease | Septicemia | Pop Eye | Treatment
*Fin & Tail Rot in Bettas & other Fish; Treatment and Prevention