Dunno. I had a tiger pistol shrimp in my biocube and every goby I put in there ended up dying within a few weeks. Water parameters were always fine - the shrimp and snails were healthy and thriving. Every fish I put in that tank died so when I tore it down I put the tiger in my seahorse tank where there was a big goby. A few days later, the goby was dead. His dead body had a "bullseye" mark on it - red spot in the center with red circle around it. I caught the tiger shrimp and brought him to the LFS. Things haven't "mysteriously" died since I got rid of him.
Sue