Red/pink worms in my tank
First time posting, apologies if I Have posted under the wrong topic. Today when doing water changes for my tanks, 2 of my 21 litre tanks I found red/ pink worms that look like a thread in a bunch (if that makes sense). I am unsure of what they are. Iíve been looking around the internet to see if I can figure out what they are but so far my research has been very vague. From what I have seen they look like camallanus but the problem is in both tanks neither have fish and from what I have gathered they are parasitic. In my shrimp tank they dwell underneath gravel and occasionally I spot them at the surface of my tank clinging onto my plastic tubing I use a as a barrier for floating plants. In my other tank that i have been cycling for about two weeks now I found them inside this white stuff that was attached to the heater when I went to clean my heater. Are these worms the parasitic ones or are they just detritus worms.
Sorry about the longs post. Any help/ advice would be appreciated!