Bugs on my plants.

[Xod]

I recently found some almost microscopic sized bugs in my fish tank. I can't take a picture because they are that small. Anyways I think having floating plants allowed them to congregate in my tank. I would like to know if anyone has any ideas what they can be. They have a very small head and a larger bottom, with a reddish tan color. I think they make be water fleas?

[Mike_Noren]

The three basic possibilities are these:
Copepods: http://fmel.ifas.ufl.edu/images/male1.jpg

Cladocerans ("water fleas"): http://mrskingsbioweb.com/images/daphni.jpg

Ostracods: http://www-eve.ucdavis.edu/stachowicz/s ... _small.jpg

Copepods are by far the most common, you'll find them in every aquarium with plants if you just look for them. They tend to be opportunistic scavengers, eating rotting plant and animal matter. The species in aquaria spend most of their time sitting pretty much still on the glass and other hard objects, going for occasional very fast swims. Basically harmless, though some species can attack very small fish larvae.

Cladocerans are the most uncommon. They _can_ thrive in aquaria, but as they're filter-feeders and favored food for many fish it's not common. Swims all the time (if that's the right term as they mostly "jump in one place"), very rarely sits still on surfaces. Harmless.

Ostracods are reasonably common, especially in planted tanks, as the most common species eat mainly rotting vegetation. Can very rarely mass reproduce and may eat holes in the leaves of some plants. Generally don't swim, but walk around, especially among rotting vegetation.