What The ?

[cliffy]

New tank arrived yesterday. It was set up last night filled with water and gravel and one oxygenating plant. Got up this morning and turned light on to admire my new tank and much to my suprise there was movement in there. The only way I can describe them is tiny white worms that wiggle like mad every now and again and then float for a bit and just repeat this behaviour. My first question is what are they ? Second one is do I need to do anything about them or shall I just leave them be ? My thoughts were that they may be some sort of parasite and could harm fish when they go in there. Must be between 10 - 15 of them in there.

 

[Aquascaper]

Planaria that have come in on the plant. Harmless and will be eaten by fish when you get some.