Thanks very much.
I noticed they came about at the same sort of time as they fry appeared - Kate said they like to eat fish eggs, but I didn't see them until the fry hatched, and also since the fry are here, it means that they haven't been eaten. Or of course maybe it's just because the fry are so tiny that I have to look much harder and closer to see them so I only noticed them then.
My betta seems to eat them - at least somebody is getting the good of them.
Well, I'll cut down on the feeding and gave the tank a thorough gravel vac and water change last night as well as cleaning the glass as usual so hopefully I won't be seeing quite so many now.
I wonder where they came from though, I know they are caused by overfeeding, but if they weren't there to begin with, I don't understand how they just appeared. Surely there had to be some there in the first place to produce all these other ones?
Good that they're not harmful though - I was panicking earlier thinking that maybe this was the return of the dreaded white spot, and I was seeing them in the stage before they burried into the fish. It wouldn't have explained the worms mind you, but it still worried me.