Something In Sandbad

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Hello everyone. Sorry for english.
I have spotted something in sandbad today while water change.
Seems the sand pops out a little and there are tiny almost transparent worm-like things. Doesnt seems to move. There are 2 different areas that i spotted them.
My tank is 30x30x30cm cube pico and its nearly 4 months old. No sump, no skimmer, no water testing just salinity.
I have 2 clown, 2 conch, 3 snails from marmara sea (turkey), may be thousand of copepods and isopods, many spirorbid worms and tube worms (or feather duster not sure about name)...
So here are some pictures. Please can you tell me what are these.

 

[BiggestE222]

Just filter feeder. No problem

 

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Thank you. Do you have any idea of what speciesare these?

 

[Goaway]

It could be either spinoid worm or spaghetti worm. If it has more than 4 tentacles, its spaghetti

 

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Jesus what a creepy creatures.
I hope they always hide under sandbad.
Thank you all.