As far as I can tell, not all of those fish pictured are zebras??? Three look to be another species.
The top picture has 11 fish and two are not zebras- the small one under the bigger zebra;'s tail and the one up the corner in the top left.
The bottom picture has 12 fish and three are not zebras- the little one in the middle of the row of three at the top, the one directly below it and then the one that is a couple of inches to the left of it. They are all clearly smaller than the zebras.
Zebras are pretty much impossible to confuse with any other fish, even soon after they go free swimming they are clearly zebras:

What makes the common person uncommon is common sense.