I’m definitely no expert, & as far as I know I’ve only had 2 worm experiences. Keeping that in mind, to me that looks more like a leech - how big is it? It looks kinda huge. I don’t know what that is, but I’m almost certain detritus worms are only tiny... and are never black. But like I said, I’m no expert so I could be wrong. Either way, the safe bet would be to use a gravel syphon to give your substrate a thorough cleaning. Sorry I couldn’t be of more help. Hope all goes well with it
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