Need help identifying "worm looking" critter seen under microscope

[GePerezReef]

Hello folks:

I suspect I have diatoms so I took a sample of my sand and analyzed it under the microscope (the sample was taken using the "10/0.25 (160/0.17)" lense with the WF10X (DIN 18 MM) attachment).

Sure enough, I do see diatoms but I also see some "worm looking" critters that I have never seen on samples of the aquarium before (I have had diatoms before).

I have been scouring the internet for a positive ID to no avail (search results are too broad).
What is concerning to me is that this was a fairly well scoped sample and yet I seem to have plenty of these critters.
Below you will see a picture and a video showing many of them (my apologies for the shakiness of the video, I had to use the cellphone on the microscope).
Any help identifying them and suggestions for control would be highly appreciated!

 

[Dan_P]

Hello folks:

I suspect I have diatoms so I took a sample of my sand and analyzed it under the microscope (the sample was taken using the "10/0.25 (160/0.17)" lense with the WF10X (DIN 18 MM) attachment).

Sure enough, I do see diatoms but I also see some "worm looking" critters that I have never seen on samples of the aquarium before (I have had diatoms before).

I have been scouring the internet for a positive ID to no avail (search results are too broad).
What is concerning to me is that this was a fairly well scoped sample and yet I seem to have plenty of these critters.
Below you will see a picture and a video showing many of them (my apologies for the shakiness of the video, I had to use the cellphone on the microscope).
Any help identifying them and suggestions for control would be highly appreciated!

Is this a new aquarium? Anything happening in the aquarium that makes you feel that you need to control them?

 

[GePerezReef]

Is this a new aquarium? Anything happening in the aquarium that makes you feel that you need to control them?

I have lost a couple of small fish. I attributed it to the diatoms but I'm wondering if these critters had something to do with it.

 

[Dan_P]

I have lost a couple of small fish. I attributed it to the diatoms but I'm wondering if these critters had something to do with it.

I never heard of diatoms killing fish.

The organisms living in the sand are typically the aquarium’s microscopic clean up crew.

 

[GePerezReef]

Thank you for the input, I really appreciate it.
I forgot to mention the aquarium is about 2 years old at this point. I am battling what appears to be cyano / diatoms.
I will leave these guys alone then and keep troubleshooting the other two problems. "
Thanks!