Leave them in there as long as they are alive. Blackworms live in water. Never leave dead blackworms tho. But if a handful of dead blackworms is enough to poison your water, you should probably have a larger tank.
Leave them in there as long as they are alive. Blackworms live in water. Never leave dead blackworms tho. But if a handful of dead blackworms is enough to poison your water, you should probably have a larger tank.