Free floating worms off gulf coast, id?

[purple fish]

Hello everyone! Recently was able to get some sand off the Florida coast and was planning on putting it in my current seed tank. I was wondering if these free floating worms were detritus worms? They’re not too quick and are attracted to light. Thanks!

 

[purple fish]

Not too hard to take a picture, but I’m guessing they’re nematodes? They do move in an up and down motion when they swim. I have an orchid dotty back and just want to make sure these aren’t parasitic. Got the water and sand from a beach. Any info helps.