I have a 55 gallon saltwater tank with a 4in. live sand bed, and a few pieces of fake coral. We have a power head (wave maker) a heater and a dual whisper filter with 2 bio-wheels. I let my tank run for a full month before adding (i’m not sure that did any good, but I waited anyway) just the other day I purchased 3 small yellow tailed blue damsels. Acclimated them just like we were told and even fed them live brine shrimp. The next morning, there was a white fish that was once blue laying dead at the bottom of the tank. Checked the levels the Ammonia was 0, pH was 8.2, Nitrite was 0, and Nitrate was 0, and the hydrometer said 1.022….The other 2 fish seemed fine and were swimming and eating …the next day yet another fish dead….checked the levels again I got the same results…now today they other fish is found dead in the same spot as the others? The pH is 8.3, so that is slightly higher but nothing else. What are we doing wrong? Anything we can do/buy that would help?