Help! What are these things?!?

[fpinto]

They show up at the base of the glass in the algae that accumulates. The only way I can describe them is they look like a butterfly without wings. A little body with two antenna. They move around very quickly. Is this bad? How do I get rid of them?

 

[ezy33]

This is a good site to identify the critters in your tank.
http://www.xtalworld.com/Aquarium/hitchfaq.htm

They are most likley Copepods.