Help IDing this aquarium critter (a roundworm perhaps?)

[biotsrama]

All right, I'll try to get an API master test kit.

It's possible these worms are so-called "whiteworms":
http://www.youtube.com/watch?v=HhWPNhI8iiU

They're too big for fry though. The worms are about an inch long.

 

[biotsrama]

My API test kit came in, and nitrates are at 0ppm. The test solution stayed yellow after 5 minutes. This was with vigorous shaking of test bottle #2 for 30 sec and the test tube for 1 min as described in the test booklet. This is not surprising, given that my tank is heavily planted, and I also run Purigen in the filter (which I neglected to mention previously).

As indicated before, I only see the "nematode" occasionally, usually around tank maintenance time. I think no action needs to be taken. But the reason I asked on here was to make sure, because if it was a parasite, I'd want to get rid of it, even if I only saw it once in a while.

Thanks again everyone!