Well, I bought 2 Zebra Danios.
However... I'm now down to one. I didn't even get the other guy into the tank.
I don't own a fish net, so when I usually get new tank residents I cut the bag and drain water into the sink (perhaps you can see where this is going).
Anyway, one of the Danios, managed so swum out of the small hole I cut... and into the drain :-\