I have started to clean my dads tanks for him. so i was cleaning the other day...and in the substrate were these worms...which i quickly looked up and thought might be bristleworms...there is no live rock in there...so our question was how did it get there? ive read that this can be postive as well as negative for the tank.. he has a trigger in there, 2 puffers, a parrot fish and a plaid fish...i cant remember the name.