[Mikaila31]

They are usually copepode/cyclops or something similar. Most all are harmless and make good fry food.

 

[Mikaila31]

Ches is right tho. Even with my bridge camera and a 10X macro lens it would still be impossible to identify anything like a cyclops, rotifer, or other kinds of copepods from standard pictures. They are not called micro invertebrates for nothing. Most tanks are home to things like these, whether the keepers notice them or not. A number of them are barely visible to the human eye if you have good eyesight.