Answer: Since we don't know for sure what the black worms are (could be beneficial, could be destructive), we can't recommend a treatment. Your best course of action would be to repot your callas in fresh potting soil, which will eliminate the soil critters. Callas need a rest in order to grow and bloom properly. There is a natural resting period that callas go through during the fall, when the leaves should wither and dry up. At that point, gradually slack off watering, and allow them to rest for 3-4 months. Repot it in fresh, rich potting soil (make sure to place the rhizomes 4-6" deep), and resume feeding and watering. You can keep your calla indoors, but you'll need to stop watering in the fall so the leaves will wither and die. At this point I'd keep the callas going through the spring and summer, then allow them to go dormant in the fall. After resting, they should bloom for you.
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