Tiny Worm Like Things On Lid Of Aquarium ?

[Jam Jam]

Just topped up my tank due to evaporation and when taking the plastic cover off noticed some very tiny bacteria looking things on the lid ? 
Is this normal and what are they ?
 
Quick picture of my tank after a few months 
 

 

[David J]

Any pics of the things you're asking about?

 

[Jam Jam]

No sorry I thought about that just after i washed it off.If they re appear I will post  a picture /

 

[Jam Jam]

There back !
 

 

[copps321]

The only thing I had was fly larvae but that was because some food got stuck and went yucky.

Sorry but I can't see anything on the picture but that's probably my eyesight lol