I only partially agree with the text. IMO I am not sure that euphylia are so sensitive to anything but stability. In nature, stability of parameters is probably close to absolute, but the corals are exposed to various elements... It's the sea guys! In our tanks, my take is that besides parameter stability, water quality is critical. That spells that the tank should be clean so that the bacteria in the water column will not proliferate too much and increase the population of the "bad" pathogenic bacterial population. The nitrate that we measure is only a final product reporting on a long trail of organic matter. So if it is too high, consider that your water quality may challenges the coral's immune system.Thread 'Euphyllia (especially torch coral) buying help' https://www.ultimatereef.net/threads/euphyllia-especially-torch-coral-buying-help.885184/