Jon, I did a search through Google and all I could find about strontium is that ir promotes and speeds growth.  Can't find any technical stuff about it.  I only looked through the first page of links though.

Mark, yes I have seen Brian's tank but I don't want be rude so I'll keep my mouth shut.  Has anyone every tried High Pressure Sodium lights?

crazy-sps, I really wasn't trying to get anyone, I was just curious.  I would be interested to learn more on how Mg helps corals to calcify.  The coral calcification mechanisms I'm read about don't mention Mg, just Ca.  The Mg in our tanks do help us to keep Ca levels higher then we normally could.  And calcifiction, both in corals and non-biological, seems to increase at higher Ca and CO3 levels.  As for where Mg goes, some of it is incorporated in the coral skeleton (about 1000 ppm compared to 380,000 for Ca).  That means a gram of Mg is consumed during coral calcification for every 380 grams of Ca.  Coralline alage has a greater level of Mg incorporated in it's growth.  I also wonder what role, if any, that Strontium plays?

Mark, the board must be counting each of your posts twice .

FYI - I used tap water for the first 3 months in my tank.  I had a RO/DI unit, but we were remodelling and I didn't hook it up at first.  I had a BUNCH of SPS in the tank right from the start.  It not only survived with the tap water, but it flourished and grew at a phenominal rate.

Since I have switched to RO/DI, have I seen any differences?  The answer is yes, I have.  The difference has not been in how anything is growing but the amount of algae that is growing in my tank.  The removal of silicate and phosphates has helped in reducing the amount of algal growth in my main tank. 

IME, tap water does not affect the health and growth of SPS.

Mark, are you talking about Brian that used to work for MSM?  Have you ever seen his tank?  Did you think it looked good?  

Frogspawn, or Euphyllia paradivisa, is not an SPS and can grow anywhere.  I think you missed the point of my post, though.  I was complimenting your tank, not trying to argue.  That is great that the sps that you have has grown well for you.  I do not think that is the norm.  I hope it continues to flourish.

I wonder if the flouride is going to do anything to tanks that use tap water?  Any ideas?

crazy-sps, 1200 ppm is good.  NSW is a little closer to 1300 ppm, but there's probably not a lot of difference as far as the livestock is concerned between 1200 and 1400 ppm.  How often do you add?  How fast does your Mg concentration drop?  Why would you want all your good carbonate (Alkaninity) precipitating with the excess Mg?  It's can become like a dog chasing it's tail.  FWIW, the Mg concentration in my little tank has not really changed in the past year (mix of soft and hard).  It appears that the food and other additives I dose provide enought, or my Mg just isn't being depleted.  Coralline algae can be a large consumer of Mg and I have plenty of coralline too.  Where do you think your Mg is going?

Jon, in response to your question about excessive additions of Mg to our tanks; Magnesium Chloride is what I add to my tank by means of Tech-M from Kent.  I try to run my Mg level about three times my Ca level.  So about 1200 ppm or so.  Even if too much is added, it will just precipitate out anyway.

Mark, I took a look at your tank  in the tank of the month.  Congratulations on such a good looking tank.  I do, however, feel bad for the clam that is gaping.  It appears to me that your interests are in soft corals.  It has been my experience that sps corals are much more sensitive to harsh water qualities.  If you removed the soft corals and replaced them with sps corals, I do not think it would look so nice.  I think they would die very quickly.  So for my application, tap water is not an acceptable solution.  You did not reply to my question about using carbon and sediment filters in-line though.  Have you had any experience with this?