I found few of these red worms after vacuuming the substrate. The are about half to one inch long and the width of a hair. Are these parasites or are they harmless? Thanks. I cut one of them in two and both parts were still alive! Did kill them within some salt though. I haven't fed any live food to my fish. I do have a lot of similar looking smaller (about half a centimeter) but white worms in the tank though and my fish love to eat those.
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