Worms in water tubs?

[JillA]

My horses have tub trugs for their water in the stables, and fortunately they are light enough for me to see that quite often, in the bottom are a small number of worms. They look like the dendro worms in the muck heap, a couple of inches long, thin and reddish colour.
The muck heap is behind the stables but there is a gap and if they should be migrating from there they would have to cross a couple of feet of grass, climb up and over an 8 ft wooden wall, through the ventilation at the eaves and down the other side. Never seen any on the walls, and I don't think birds are bringing them in but it is just possible.
Any ideas? I have found them on several days, washed out the tubs and refilled.......and there are more again.

 

[Pinkvboots]

I get worms in the field water and soaker but never in the stables wonder how they are getting in do you think it because of all the rain we have had

 

[Chinchilla]

following.

 

[Elf On A Shelf]

Birds. They drop all manner of things in water buckets whilst dropping in for a drink.

 

[Shay]

Could they be bloodworms? They are in fact midge larvae not a true worm per se. The midges lay in still clear water and your stable buckets are going to be warmer than any other still clear water source just at the moment. They won't harm anything - just wash then out (or feed to fish..)