Last reply on the subject from me, and then I'll leave it alone. This is meant in a spirit of addressing the scientific information below, and not at a personal level, and I believe that Heinz' comments were given in the same vein.
I'm sure there are situations in which the level of Ca can be dangerous, and that the equations below will make sense. And certainly keeping levels of any primary parameter greatly above the ranges recommended will, over time, cause problems. The issue is really the current tank situation, the level itself, and the amount of time you do it for. Life is made up of guidelines, and not as many rules, although there are obviously some very specific ones in reef tanks. Just as some tanks will live at pH 7.8, others will not, and prefer the normal 8.2 or so.
The proof of that is in my tank, which was low in Ca and Mg, and high in Alk for a while, has completely turned around over the past few weeks by bringing Ca and Mg up to the levels I have, and I have also seen a consequent drop in Alk. Or perhaps I should say that by lowering Alk, I was able to bring my Ca and Mg levels up to where they created a stable situation.
Without being a marine biologist, and a long way from high school science, in our case, the higher range of Ca and Mg has been beneficial to our tank to enable the Mg and Ca starved animals recover and absorb these elements. By absorption of higher range values, the plentiful supply of Ca and Mg was beneficial for a while. Now that we have seen a recovery, it's time to back these values down to the recommended ranges.
I'm as certain that keeping the range high for a little while was much safer than slowly bringing it up to normal and leaving it there. If we had not done what we had done, I'm certain most of our tank would have been dead. Am I right? No one will know. But the proof of viability is in the success. This one worked for me at this time, under the circumstances I had. Dangerous? I don't think so. Ca at 600? Probably would have caused the same problem as Ca at 350 with high Alk, but 500 was safely high enough to ensure availability and was quickly absorbed to bring the level down during the periods between changes. Now my tank is stable and properly metabolizing Ca, Mg, and keeping Alk at it's lowest levels since we've started.
Finally, going back to the reason for my intial post in this thread, our biggest win was measuring the NSW before introduction to ensure levels which would manage to bring us to balance. With our water change today, we're able to see normal tank processes we hadn't seen before and keep much better control of mineral levels. Every step of learing is helpful, and for us, the last 6 weeks have been huge with our tank.
because I've been on vacation). Then just for fun I tested the newly mixed (Monday night mixed) salt water. It's testing at 360 right out of the bucket. This is only the 2nd mix from this bucket so does this mean I have a bad batch or something? The bucket is badly scared on the outside so I can't read what the label says. 
