Worm!

[PNA]

Yesterday I was looking in my tank and I saw what looked like a small worm slowly moving down the front glass of my aquarium.
I find this somewhat troubling.  I have never fed my fish any kind of live food or dried worms, only flake food.
The worm itself was no more that half a cm long and maybe 1mm wide.
I've got a few rasboras and shrimps, and a bunch of malaysian trumpet snails in the tank, and it's somewhat heavily planted.  I've also been keeping it mostly dark in order to remove a small algae problem (couple hours of light per day for almost a week).  I've had it up and running for around 3 months.
I'm hoping someone can tell me what it was, and what I should do about it.
Thanks.

[dpatte]

there are various creatures that can come in via plants, fish or water. In your case it sounds like some form of flatworm (planarian) and is quite harmless and common in most lakes and rivers worldwide. There are many types of planaria, but they mostly look alike - and only vary in size.

Look up planaria on the web and let us know if it matches what you are seeing.

[PNA]

Sounds like that could be it.
This last week my fish wouldn't eat much at all, I guess because they weren't used to having the lights off for so long.  I'm sure I'd try to compensate by feeding them more.
I'll try to clean my gravel... or will my plants and snails absorb the excess food.
I guess I should test the water and if it's bad I'll do something about it.  Otherwise I'll let things be.