I really think 10 g is even too small for catfish, as most of the smallish ones are schooling fish so you can't jsut get one and expect it to thrive. They have a HUGE bioload (omg, plecos can poop!) And some bettas just hate them to death (literally, in my plakat's case, he's killed a couple of tankmates so far..).
What about some shrimp? They're fun to watch and provide entertainment (and the occasional lunch) for my bettas. I stock half a dozen RCS every six months or so in my heavily planted 3.5 gallon. Also, a few in the 10 g with my large plakat (ofc, they don't last as long with him..) The shrimp get picked off by my aggressive little VT girl every now and then and eventually all go missing but I don't mind - the bettas are in glowing health and happy, my plants and wood are algae-free and shrimp don't have a huge bioload so it doesn't matter if there's a few still hiding out when I restock.
I recently got some Darwin Algae Shrimp for the 3ft wild betta tank - these are native to Australia (I hope they end up in America, you guys would love these shrimp!) -- they are a lot like ghost shrimp, larger than RCS and a bit more aggressive. After a couple of swift nose-pinches, my wilds have decided that picking on the DAS isn't worth it, and now they all get along. The DAS are great to watch toodling around and changing colours every now and then.. and yeah, they love the algae. Shrimp are really win/win (well, maybe it's not so win for the RCS in my splendens tanks but everyone else is pretty happy, heh).
Last edited by Aus; 08-18-2012 at 12:24 AM.