hello, our main tank has been running now for around 6 months. We set up two small(60 litre) quarantine tanks,one for fish and one for frags/corals etc. We used tank water from a water change to fill both tanks and decided to buy some livestock. We bought a Royal Gramma,a Starry Blenny and a Suntail Goby/Pistol Shrimp pair. We put the fish in one tank and the shrimp and a few frags in the other. All fish ate well for a couple of days then one by one all three died. They were breathing fast and eventually just being blown around in the current until they died. We stripped the tank down completely,cleaned it all with vinegar,let it dry and left it for a couple of weeks before setting it back up again.On Saturday,we picked up another Royal Gramma and a Starry Blenny from a different shop to the first time and on Sunday,another Suntail Goby from another different shop. When we got back with the Goby,the Gramma was dead. The Starry was eating like a pig for two days then has got really picky and the Goby was not eating. Today the Goby died and the Blenny is breathing rapidly. Can not for the life of me think what is going wrong. The water parameters all seem good and the critters in the big tank and the corals in the frag tank are all doing well in the same water.Anybody have any ideas,i hate seeing things die!