most active

[gmh]

Silvertip Tetras may be the most active small fish I have seen. Not the best schoolers but they are constantly chasing each other around the tank, pairing off and fighting or spawning

 

[jm1212]

pretty much any species of danios, including CPD's
tiger barbs for sure
clown loaches
angelfish
platies
guppies
mollies
most types of gouramis

well i think it would be easier to pick inactive fish...
plecos.

 

[stezatois]

my rainbows dont stop moving, nor do my zerbra danios, leopard danios, My CAE's are super active, tho they do have down time too. The boitia striata (zebra loaches) are active and out a lot too for something active in the lower end of the tank.

 

[Dangerdoll]

I'm going with Rasboras too, they are always flitting somewhere and always together. I would include Rummynose Tetras as being similar...

 

[vanillarum]

My sids are like energizer bunnies ! They go for hours, take a break, go for hours, take a break, etc, etc.

 

[Dean]

sids = dwarf loaches