Hello Everyone, Can someone please help.I made some major mistakes.I have had my tank up and running about 5 months.It is a 44 pentagon. I had 6 damsels in it.My husband brought home from the ocean a couple of trigger fish.It seemed that everything was fine for about a week. I did my monthly 1/4 water change.Everything a couple of days later started dying off.(They were all hanging out at the top of the tank.) All my fish died. I took a water sample to my Local fish store they said all my parameters were good except my salinity, they said that it was 17. They told me that that is not what killed my fish. I bought 6 more damsels and a couple of very small hermit crabs,While floating they I increased my water up to 23, everyone seemed happy.They were all eating. The next morning I got up some were dead. The others were breathing very heavy.Could the salinity being low have killed my original fish and the fact I increased my salinity have killed my new fish? I also at the time of my water change obtained a couple of pieces of live rock from another fish store.I donn't know what to do from here.I threw my old salinity tester out and bought a new one.Seems the old one wasn't working.