I read an interesting article the other day regarding the fluctuations alot of coral recieve depending on location of collection. It implied to me that some fluctuation in parems might actually be a healthy thing for captive displays. It conditions the coral for fluctuation, and makes for a hardier coral overall. People usually speak of the ocean being such a constant environment. It really depends on what area of the reef the coral was collected from, IE: SPS being completely exposed to air for hours at low tide; some isolated patches that experience evaporation/temp fluctuations at low tide and then are flushed with fresh ocean water at high tide (lagoon type), etc. Knowing where your coral is generally found on what part of the reef is important.