This is my first post here, here goes...
On several occasions I have noticed a thin, white worm in my 30 gallon planted tank. I have never seen it on a fish or on glass; I have only seen it wriggling in the water, undulating its body in a whip-like fashion. It seems to show up after I disturb the tank (e.g. water change or cleaning the filter). The following video is not mine, but is a good illustration of what I've seen:
Note that the video also shows a planarian FLATworm crawling on the glass; that is NOT what I have in my tank. I have the thin, white undulating worm shown in the video, which I believe is probably a ROUNDworm, not a FLATworm.
The fish haven't shown signs of sickness or anything (I've had the tank for close to 5 months), but I wanted a positive ID on this creature just to make sure that it's nothing to worry about. I have a hunch that it may be a nematode, but that is only my guess. Water params are pretty standard (0 ammonia/nitrite, < 5 ppm nitrate, pH around 7).
Much thanks for any insight you could provide!