Over last week a lot of little white worms have appeared out of nowhere in my chinese algae eater tank.

Cant take a picture as theyre too small.

Don't know where they came from, not added anything new, water fine, tank clean.

Are they anything to worry about?

2-3mm long? look like bits of white cotton thread? Do they wriggle in the water current? Do you use a gravel hoover?

Probably planaria. Completely harmless, my fish eat the odd one I ever see quite quickly. Usually a sign of overfeeding (they are scavengers) and lack of hoovering the gravel enough.

Cut back on feeding and give the substrate a really good clean when you next undertake a water change They should reduce drastically. I'm assuming you've posted in the cold water section by mistake? These are tropical fish of course http://www.fishkeeping.co.uk/modules/ ... sheet.php?caresheetID=126

No posted here purposely, that caresheet used to be in coldwater section and it does say "fine in cold water"

Yes the worms are as you described.
I do use a gravel hoover, last water change i thought there was excessive ammount of waste sucked up so could probably be problem.

Thanks

Some of the care sheets here still need a bit of an update TBH. They are happier in 24-25 degrees as far as I'm aware. Some suggest they can tolerate temps down to 22 but I'm very dubious of this.