What are these id please

[Colgan10]

Not sure what these are my brother set up a tank it is 5 months old he has added dry rock one fish algae barn cheato and pods, Coraline algae from arc reef and a could snails. I’ve never seen them before there are a bunch they are some kind of worm they are small and have frills on the end anyone know what they are only pictures I got so far.

 

[kchristensen8064]

Hard to tell from the pictures since they are blurry, but going off the description I'd say spaghetti worm possibly.

 

[dbowman5]

if the tentacles are like threads it could be a spaghetti worm; if they are like antennas with branches it is a cucumber like a medusa worm, beneficial filter feeder. I have generations of them

 

[Colgan10]

if the tentacles are like threads it could be a spaghetti worm; if they are like antennas with branches it is a cucumber like a medusa worm, beneficial filter feeder. I have generations of them

That’s 100 percent it in the picture! Thank you I will let him know