Making a suitable seawater standard is actually not that easy. I do not agree that using calcium chloride alone is suitable since it presumes a kit designed for seawater will be properly checked by a calcium in fresh water standard.

Just learned of this Tuesday 1-9-08, I have been using RC from DFS in 160gal buckets, started to notice 325 Ca last summer, thought it was me, I bought 3 buckets in Oct from them when I took a road trip up to there store. Just got into the first one, Ca325, sent samples to ASI yesterday, disapointing.
Bob

Randy,

So how do we go about determining the accuracy of our analysis? I understand that seawater complicates things but a reliable standard sure would be helpful to this discussion. As a practical matter, is that possible for the hobbyist?

I'm comfortable with what I am doing. When my test kit indicates Ca concentrations around 350 ppm or less, my corals don't grow much. When the test kit says 425-450 ppm, they look good and grow well. I guess I really don't have a precise measurement of my actual Ca concentration, but as long as IO and test kits are consistent, I suppose I don't really need to know. Just makes it hard to compare with others.

Randy,
after reading all this and about test kits, what is your opion on the Salifert Ca, Mag and KH test kits? I may switch to them now that DrFS are carrying that brand.
Bob

I still use Saliferts for Cal Alk and Mag. Reasonably priced and easy to use. I'm not having any problems with accuracy. Still the best of the hobby grades IMO.

API has also given me good numbers but they don't make a magnesium kit and the results are a little more general.

Randy will probably tell you he doesn't test much anymore because he hates testing. :lol:

I'm glad to see the good Drs carrying Saliferts now. :)

Billy,
DRS will not have them in until the 15th according to there website, but they are 1/3rd cheaper there then MD.
Bob

Probably a promotional thing. I buy from both companies and have always gotten good service from both.

DITTO, but better luck with LS from DRFS.
Bob