I have a ton of kuhlis in my 30G, but I don't know if I'd put them in a 10G--I just imagine them being cramped. They're also very shy and love digging into things--sometimes I don't see them all day. With a predatory fish like a betta, I don't imagine they'd stay out for very long during the day. Also, if you're thinking of using any kind of resin/plastic decorations, use extreme caution. Kuhlis love burrowing and getting into tight places, and they will get trapped and die in the most surprising places--I would advise natural or solid ornaments only.
After having ADF once, I don't think I would get any again. They are very difficult to feed and would have to be fed separately from such an opportunistic fish as a betta. Aside from the simple logistics of feeding them, it's also difficult to satisfy their dietary and water quality needs--ADFs can live to be upwards of 15 years old in an aquarium, but many only survive months. Having 8-10 in there would be extremely impractical and cramped, you might get away with maybe 4. They also aren't really that active--mostly they just sit around in weird froggie poses when you can see them. They had my mother convinced they were dead a few times, lol.
Personally, I think a school of pygmy cories would be best, they won't attract attention from the betta, but they'll be active and out all day and give the tank a lot of movement and interest. They're also super adorable and have a lot of personality.
Last edited by Adastra; 07-14-2010 at 02:16 PM.