Two things I just found...

[mikst]

This one I found while moving things around in my tank. It looks like a big freshwater pond snail. Moves fast along surfaces.From the hitchhikers guide in this forum maybe a stomatella snail?

The second ones are very small, less than 1cm long. Very dark. They move along like earth worms (squishing themselves up to be short and fat then extending to be skinny and long), not moving like inch worms or leeches.

 

[cloak]

The second picture is a Stomatella snail. (good) Not sure about the first one though.

 

[TeamAquaSD]

The second picture is a Stomatella snail. (good) Not sure about the first one though.

I second this. Not sure about the first pic but 2nd is a stomatella and a nice little clean up crew member

 

[mikst]

Cool, thanks.

 

[OrionN]

The first is some kind of bristle worm. Does it has hair on the side? Segmented or smooth?

This is a baby Bristle worm

 

[mikst]

I have bristle worms in my tank and it looks nothing like them. It looks like a live blood worm honestly.

 

[OrionN]

Perhaps it is a Spaghetti Worm