Thusly "Chris Lutka" Spake Unto All:

From a Google image search of the nematodes, it appears that we may
have those creatures. Although some websites state that they only
reach 5mm long, I know we have longer ones upwards to 10mm.

Oh, nematodes can reach _8 meters_ in length (the parasitic whale
roundworm). Non-parasitic nematodes are usually very small, often
microscopic, and they're found everywhere. There's hundreds of
thousands in any given aquarium.

The easiest ways to separate nematodes from small aquatic earthworms
(also very common in aquaria), is to a) check if they're segmented
(nematodes aren't, earthworms are), and b) check how they move
(nematodes thrash around wildly, earthworms move like, um,
earthworms).

Also, if the worm's got any bristles, then it's likely an earthworm.
Very few nematodes have bristles.

A small aquatic earthworm may look something like this:
http://www.inhs.uiuc.edu/~sjtaylor/cave/cave_olig.jpg

Whereas all nematodes you find look like this:
http://www.altgarden.com/site/pestco...s/nematode.jpg