Fry or foe?

[Theodosia]

I have been vacuuming small "bugs" out of my tank and watering my plants with them. They appear to be very small sand fleas.
Now, I have 2 baby platys (at least I did last night) and wonder if I've been sucking up babies.
What do fry in the early stages look like?
Or, what kind of bug is this?
Are they harmful?
They sure are busy...

 

[Dragonslair]

It sounds to me as though you have been sucking up fry. When livebearers are first ejected the are very small but fully developed replicas of their parents. The may be transparent but they swim by darting away. Unlike daphnia(water fleas) that hop away. Probability is that you have sucked away fry.