i've seen many a betta jump to it's death.it's hard for a fish to realize that there isn't water outside of it's cup
stupid cups
i would check into the azoo palm filter or the red sea microfilter,or you could even check out one by a company called capson enterprises i think,i don't know i seen an ad in tfh but now i can't find the issue.i have seen first hand the azoo and the red sea filters and i think both would be fine for a betta.as a matter of fact when i seen the red sea i think the first thing i said was "i want one".
if you have the same two gallon hex that i do,you'll find that the cover is easily modified with a hacksaw,a razor balde and a nice file.
on second thought at the cost of a microfilter you could get an explorer eclipse2 and never have to sweat it.i think they make great betta tanks.the filter is rated at 35 gph and comes with a biowheel too.and to boot i think they have been retooled to have a small light too.mine was $26 dollars at petsmart and they run about the same or a few dollars less online.
if you find the flow is too much for your betta just put a plant or tow right in front of the return,problem solved.live or plastic is fine.if you use live java ferns are best as the can be bought tall enought to block the return and will get by with room light.if you use plastic just make sure the plants don't have any sharp edges to rip your bettas tail.one more cool thing,they run about 74 to 82 degrees year round.no heater needed.