There seems to be some confusion about Bettas and houseplants in water.
I've bred Bettas for decades, I've written for various aquarium magazines for ages and started all the tropical fish fora (mail lists, newsgroups, websites) in the early Internet. Any good book on internet history will mention me.
It may come as a shock to some people that some terrestrial plants can also grow in water and these have been used in the aquarium hobby for - literally - centuries - to clean the eater by removing ammonia. They're fine and don't "need oxygen". Water roots are different from soil roots, some plants such as peace lily and pothos (and others) can grow water roots, which most plants can not.
Even less people understand Bettas. These fish are in family Anabantoidea and all members of this family breath atmospheric air, not water. In fact they lack functional gills!
Waste from fish in the form of ammonia, kills fish more quickly than anything else. It does this by attacking the gills and making them unable to exchange gases.
This is why Bettas and all other Anabantids can be kept in tiny containers without filters, air stones or any water movement.
In fact, they prefer and need this.
Because they have to reach the surface to breath any water movement inhibits this.
In fact the worst thing for a better is a deep tank with fast flowing water from a filter and other fish.
They are best kept alone, in non moving eater in a few inches (at most) of eater. This is how they're found in nature.
If you look you will never see Bettas in the wild in more than 5" of water or in water that moves or in water with other fish.
There are many incorrect articles about this on the net by peope that don't really know what they're talkig about. According to them, nature is wrong. Given a choice between a novice with little experience writing a blog being wrong, and nature being wrong, I'd go with the former.
Bettas have been bred for over 500 years in tiny containers. Well meaning aquarists that put them in deep tanks with tiger barbs and fast moving water is what kills them, they nominally live theur entire lives in half a liter of water.
Look at any commercial or profession breeder set ups. There is an International Betta Congress - just ask any member.
Any decent book on Betta splendens will explain this.
