They may be leeches! They do come in different colors and sizes. Some are black and some are red. Some are flat and some are round. Google some pics and see if you can spot yours. If you put it on your finger and it starts sucking your blood after a few minutes then you'll know. :-)

Just curious, did you add anything (like fish) to your fountain recently?

**Do not consider this post to be a solicition for a position as a leech tester!

No, I haven't added anything ever. I think I forgot to mention that while I had them inside to watch...like the next day they turned into tiny tadpole looking things. By then I just said "ugh" & threw them away. My grandson thinks they could be mosquito larve....
I did check the leeches search, I don't think that's what they are.

Does it really matter what they are if they are gross? I used to clean out my birdbath with clorox water. Leeches - yuck!

That's what I clean my fountain with also.

They are probably bloodworms. Many people use them as fishbait.

Bloodworms are midge fly larvae. Midge flies resemble mosquitoes, but do not bite.

Google it & see if that's what you have. They are icky - but harmless.

Bloodworms. Great fish food!

This was an entertaining thread. :-)