i'd be hesitant, especially with annuals, since you'll have to rely on their eggs to continue your tank, and i'd imagine killi eggs would make a tasty betta snack.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger-all down here on Earth.
Loki/Grendel/Gail/Beowulf/Camilla/River/Bathory/Arwen/Lafayette/Deb/Jack Skellington (soon)