i've also heard of some people having success keeping bettas with endlers, since they're so small that the betta doesn't recognise them as a "threat fish" but at the same time too big that they don't see them as food either.
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)