guppies do best in groups of three or more, glofish (zebra danios) can be aggressive in groups of less than five. i don't have any experience with barbs or plecos but i have had platies in groups of both two and three, and the seem to do better in threes. i would pick one species to cut from the lineup, and have well proper schools of the others.
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)