tadpoles

[pedrobedro]

what do second hand ones look like

Small frogs probably

 

[bigegg]

be fly larvae if its in a bucket I get em if I leave buckets out with dirty stagnant water in . tip em out

If you pour em through a pair of tights, then decant into a jam jar, theyre worth a bit to anyone with an aquarium.
I used to catch em (early 80s when i was early teens) and sell em to the local pet shop for 50p a jar.
I took a pay cut when i got a paper round

 

[Keith 66]

Long time ago we filled a mates wellies with tadpoles then dared him to put them on. He did.

 

[Wozzaaah]

They will be larvae, not tadpoles, we recently had similar in a wheelbarrow that had been left out in the rain.
As has been said, if they're only 5mm then you'd also have loads of jelly in there if they were tadpoles as they'd be newly hatched.