I shoot for 1.025 but IMHO
its not what the SG
level is its how stable the level is. I honestly dont care if you keep your tank at 1.020 or any level between 1.020 - 1.030 as long as its stable.
Stability is the name of the game in reef tanks. For fish only tanks a lower salinity has been said to ward off parasites where as a reef tank usually shoots for a higher salinity due to the corals. If your tank is stable at 1.024 and does not swing much than thats just as good im by book as a tank with a SG
of 1.025. .001 change in salinity is NOT going to make a tank crash or be a great sucess. If this was the case then what about the coral reefs that are close to the shore when there is a big rain storm and there are significant amounts of 1.000 water flowing into the ocean. There will be areas and periods where the SG
changes. Often times during high tide corals are left high and dry above water or they are left in tidal pools where the water evaporates over the period of low tide causing the salnity in those small tide pools to increase only to have the salinity change once high tide comes back in.
If .001 salinity was that big of a deal than you would not find corals in tidal pools nor would you find them where large bodies of freshwater dump into the sea to cause periods of lower salinity.