Actually, natural sea water in the vincinity of most coral reefs is around 35ppt, or roughly converted, about .025. I think that if you search around here, you will find that many people keep their reef tanks at .025 Personally, i have noticed a difference in coral health as well as animal behavior once i raised salinity from .023 to .025 Others on this BB have also stated that they had better luck even with little things such as snails staying on the glass when the salinity was closer to levels found in NSW.
For FO tanks, the rules are slightly different. It is more widely accepted to have a lower salinity, and the reason being, at least as far as I can understand is that the lowered salinity levels make it harder for fish parasites to live. This is also the same reason why many people put diseased fish into hyposalinity treatments.
Try doing a search around the board, or if you like, post a poll. I think that you will find that there are many people, including myself who keep their reef tanks around .025, maybe even .026. I too have heard that .023 is the limit, but I believe that this is from LFS employees who are more concerned with disease outbreaks in fish, but are also interested in keeping their invertebrates alive. .023 I am going to guess is a median between the two.
