Hello All, so yesterday I got some fish online (a few chromis and hawkfish) for my 125 and within like 6-8 hours they were dead . I have a few fish in the tank already that I've had in there for a months. So I'm trying to figure out what I might have missed chemistry wise that would cause the new fish to die but the water not be so bad that the old fish are ok ? So with the new fish I of course acclimated them for over a hour( float bag in tank first, then put in bucket and slowly add water from tank every 5 minutes for about a hour then net and put in tank). Salinity around 1.020, temp like 76, Nitrate was 33, and PH was around 8.1. I know my KH is high and phosphates are high and the magnesium is low, but I've been adding magnesium increaser to try and get it to increase so it will hopefully level off the KH. Also I didn't think either being high was fatale to fish, especially in such a short amount of time. I had been having a issue with parasites and had previously used some ParaGard which dropped the PH, but that was last week and since the I've been checking daily and adding increaser if necessary and it's been around 8 for several days. There was still ParaGard in the water as the directions said to treat for like two weeks and I had a couple of days left. But I've never had ParaGard stress out fish enough to kill them , especially in like 6 hours. Any suggestions on what I might have missed or what I could test for would be appreciated. Thanks!