Kevindo123 thanks for the replay. My salinity is 1.026 and the Alk ...i don't know coz i have no kits for that. My aquarium its a low tech biocube and i use tap water as per the my location (Qatar) the tap water is desalinaizd sea water and all the LFS they do ther SW tanks with tap water. My nitrate are high....arownd 30-40, but evryone seams to be ok...only the hammer coral died. But my problem is that if hi died it will damge all the other corals?