all time top 3

1) Corydorus Panda - My third cory variety and the tightest schooling I've ever seen, they often do syncronized glass running, its fun to watch!

2) Penguin Tetras - Kind of surprised me, but even in a ten, these guys tend to at least hang out in a clump when the light is on, when the light's off they dive for high cover (I use a fake plant minus the base that floats).

3) Cardinals - One of my LFS's had a large planted tank with these guys in it, it was lovely.
 
I agree, Columbian tetra, is #1 for me, Love their color. Then cories, I like how they lounge around in groups. Number 3, harlequin rasboras, I like their colors.
 
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