I believe these are a nematode which are harmless and will benefit the vivarium.
I had some crawling on my glass front after I got mine all set up. It concerned me too.
You might be able to find my post asking the same question and the answers from more experienced members.
I did find this information: "nemerteans are very common in the vivarium. they are a small white worm looking creature with a long pointed snout. they eat decomposing matter and insects (dead crickets, etc) they are not harmful to your animals." ( White Worms in natural vivarium.. )
Or they could be fungus fly larvae. I had many of these pop up. Eventually they went away with the help of my leucomelas.
After I got my frogs they enjoyed these flying little snacks.
Either way I think they pose no threat.
Other members might have better information though.