There actually is a short-finned variety of male bettas, but they wouldn't peacefully swim around in a tank full of other males. They would fight.
Also added some sand from the reptile department. Nobody seems to stock sand for freshwater tanks - only saltwater. Tropical fish stores also stock stuff called "substrate", which is finer than gravel but not as fine as sand, which is used for rooting aquatic plants. What I needed was fine sand for the algae eaters to hide in. Also, betta and gouramis come from ponds with muddy bottoms. I didn't want to haul in mud, but did want something finer than gravel.
After snagging the bettas, I went across the street to Home Despot and found a really nice office chair with super back support, which I am sitting on as I type this. It has a microfiber suede-like texture, silver grey. Nice and sturdy. I have not attached the arm rests, since they just get in my way. It feels a whole lot better than the one in the picture previously posted.