For information on rearing daphnia to feed fish, go to the Daphnia FAQ . A visitor pointed out to me that this site no longer works. A drawing of a daphnia can be seen at this water bug site . Euglena Euglena are green animals that many larger microorganisms, like daphnia, consume. They are a blob with a tail.
Euglena make the water appear green.
Gastrotrichs Gastrotrichs are microscopic animals that live in bottom debris attached by tail secretions. There are 60 species that live in freshwater where they eat algae. One species is Chaetonotus anomalus . Infusuria I have read that infusuria is simply a mix of microorganisms, mostly paramecium. As I get more time, I will look further into this.