Just in case anyone was interested in solutions to getting critters into a betta bowl to help keep it clean--
I happened to recently read on the web that bettas seem to tolerate those little catfish that scurry around the bottom of fish tanks. The page said the minimum number to get was two cats, preferably 3. My betta lives in a clear punch bowl that's about 2.5 gallons, so I got two little catfish. The page said to give them a place to hide, so I broke my big ceramic "cave" into two parts, creating more places to hide.
The cats hid for days and froze whenever the betta (a male) came around when they were out, but eventually he lost interest in them. Now they scurry around and he ignores them most of the time--unless they start sucking up his bubbles, which they seem to enjoy.
They have really kept that bowl clean. I feed blood worms and uneaten bloodworms can junk up a tank, fouling the water. Now the little cats just gobble up the debris and the water stays clear. They also keep clean the aquatic plants, which get brown growth if not washed fairly often.
Ta-da!
