Water fleas or other (edible) bugs?

I am 'fattening' up a juvenile mahachai female in a breeding box. Since we were going away for the Easter holidays, I decided it would be better to put her in a tank with lots of live plants where she could snack all day long.

Now, I did not empty this box before leaving, just disconnected the air line. Tonight I noticed that there are very small white things with a tail zooming around the box close to the bottom.

I can only tell by using a magnifying glass that they have a small tail.

Does anybody know what these creatures are? Should I be putting some fry in the box to let them feast on them?

Sounds like Copepods. They are small specks that have a tail, and look like shrimp from Spongebob.

Most of the time, they will by Cyclops or other copepods, as Alex noted. One word of warning, not based on my experience - some hobbyists have considered some copepods as fry predators. I have never seen this, and I have seen many similar creatures in my tanks. I have noticed that fry don't seem to eat them - adults of small species will.

Thanks for that info! Then I will put the female mahachaiensis back in so she can get some extra proteins.