Red worms in my tank, any ideas?

[Swred5]

I have a 15 gallon tank that st one point had 10 male guppies and endlers. Slowly over the year and a half they all died off except for 1 little blue endler. Over time I have added 5 false julli cory Dora's who all seem to be doing great. I reently added 6 green neon and a dwarf Honey Gurami (blame Irene's video) and did a water change the day after I got them and noticed a couple of these red worms on the glass inside the aquarium.  They were approximately 2 inches long and went down and burrowed in the sand. Is this something that needs to be eradicated?  Are they harmful to my fish? At one time I had at least 30 red cherry shrimp that slowly disappeared, I figured the snails were part of the problem. I do have a TON of snails, I feed to my puffer, incase that info helps. I'm freaking out as I have an irrational worm phobia and am freaking out about sticking my hand in there. Thank you for any info you may have. Amiee

[Fish Folk]

Hmm... interesting 🤨 

My first instinctive thought is “live bloodworm” or “live black worm” But they’re a bit different looking.

Then I found this video:

Also saw this video... treatment tips — not as helpful with diagnostic: 

 

[Swred5]

I was listening to Cory's latest live chat video and someone asked about a 2 inch red worm that looks like an earthworm. Sounds like my worms right? He said it sounded like Detritus worms and were beneficial.  I appreciate the video rec, gonna go check that out now!