Enrgh... UGF are ok, what you will want to do with it is aim the outputs about fourty five degrees from directly back to the sides. Getting reliable flow at the low currents betta like is "touchy" sometimes.
If you can find it a simple Hydro-Sponge filter will do all the bio you ever need for the little guy. They run like $6.00 online and $12.00 in stores.
They're weighted little stands with the sponge around it and a bubble pipe off the top and you can put carbon heads on top just like UGF. It'd be easier to maintain than a UGF and would let you plant as well. The small ones are about 70mm in diameter and you can use the pipe on them or add a longer pipe to reach the surface if you use the carbon cap thing. The Hydro-Sponge I'm referencing is the right height in-bag for a standard 5 or 5.5g tank.
Other option is Tom's makes a yellow round sponge thing, real cheap build and not exactly pretty but they work.
I don't like UGF because of the mulm buildup under them.