most active

Giant Danios would be on that list.
 
The most active fish in my tank are my emerald cory cats. They are all over the place
 
harlequin rasboras. i now have a school of 10. for the most part they all swim around as one. pretty cool to watch.
 
I've seen a couple SAEs and otos who would not stop moving for 2 seconds at my LFS. But I think that danios would be on the top of that list.
 
Giant Danios are crazy skittish fish.... A few popped out of the tanks in Petsmart... One hit my head another time one plopped right inside of my shirt. Very very ravenous fast eaters as well.
 
I second the harleys. Get a whole school. Mine love to "surf" in the filter current and its a blast to watch.
 
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