Hey, dude. First you should make sure, that it's worm. I mean, that there are situations, when grass can look, like the worm. If you are sure, that it's worm, then it's better to take it out of your aquarium, because it can be harmful for your fish. I don't think, that you want to risk, when it comes to dying of your fish. In fact, some worms can look similar and be as good, as bad ones, like fireworms ( click here - https://arcreef.com/bristle-worms/bristle-worms-fireworms/ if you want to read more). You know, discretion is the better part of valor.