very small worms in gravel

Good day

I reacently bought a tank from soemone. It had water in it and I currently have fish in the tank. When I was cleaning the gravel the other day I noticed these small worms in the siphon pipe. Can only see them when there is light behind the pipe.
I must add that the fish in the tank are very happy and healthy

They are about 1cm long and not even a mm thick.

What are these worms?

Thanks

 

Planarian worms most likely. Most often associated with overfeeding but occurs naturally in most tanks. Harmless to fish but can be a pain if you are trying to breed because they burrow into eggs. Unless you are infested with it you shouldnt have any issues

 

I had small white worms in my tank once.
Turns out it was from over feeding and using under gravel filters.

I personally hate under gravel filters as they are pron to issues like that.

 

Most likely planaria worms.

 

In an aquarium book I have they say that Flying Foxes as well as Blue Gourami's will eat planarian worms.