Cleaners do not need to be in a pair. They are bisexual. If they were, they would fell more comfy and showy. But, what killed your other cleaner? Was it your Temp, trate, Trite, Ammonia, pH, salinity, not aclamating long enough,ect? You have to find out what killed him. If something is wrong with your water, get the shrimp out of there! Before you get any other invert, find out what killed the first one.