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For what its worth, here is an exchange I had with Bob Studt of ASI back in the spring of 2005. He provided excellent customer service and I cannot fault anything he said or did. The only issue was that my readings never matched up with what ASI said they were supposed to be. I finally gave up trying and figured as long as the product was consistent, I could make up the difference myself. For all I know, its my test kits that read consistently low, although I kind of doubt that since I have never had one read high and I have probably gone through a dozen kits.
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Me: Changed to Reef Crystals after using Instant Ocean for over a year and was still disappointed in Ca concentration. I over-did the first batch of RC and wound up with a SG of 1.027 (calibrated refractometer, double-checked with hydrometer). Calcium was still lower than desired: 325ppm with Seachem kit and 350ppm with Salifert kit. Testing was done 3 days after mixing, solution was clear, looked normal, no unusual sedimentation. Results from the standard that came with the Seachem kit were exactly what they should be, so I doubt the test kits are far off. Over the past year, Instant Ocean was always around 325ppm Ca at SG 1.024 with Salifert kits (more than one kit has been used and the results have been consistent, they always read a little higher than the Seachem kits). At best, Reef Crystals calcium concentration is only marginally higher than Instant Ocean, not what I had hoped.
ASI: At 1.027spgr Reef Crystals should have a calcium concentration of ~460mg/l as Ca++. Instant Ocean at 1.024spgr should be at ~370mg/l Ca++. (levels at natural seawater spgr of 1.026 should be ~440mg/l for RC and ~400 for IO) I have been testing both of these products daily for over 10yrs and I find the levels to be consistently within the expected ranges.
ASI: Mr. ###, I apologize for the delay. I did receive and test the sample a couple weeks ago. At a specific gravity of 1.024 (32ppt salinity) I found calcium at 392mg/l Ca++. This is actually at the low end of our acceptable range for this spgr but it is within specs. This level would be at 429mg/l Ca++ if the spgr were raised to natural seawater level of 1.026. Our target is 440mg/l Ca++ at 1.026spgr (35ppt). I will be happy to send you a bucket of Reef Crystals as well as one of our SeaTesT calcium test kits for your troubles.
ASI: From a Seachem reps response on an online bulletin board I learned that the calcium standard they supply is simply seawater made from their Reef Salt sea salt product. The seawater is prepared to the predicted salinity that should have 400mg/l Ca++. This is not a very reliable way to make a standard. If their Reef Advantage Calcium is a dry product it is probably calcium chloride, either anhydrous or dihydrate, and would be a better source for making a standard. If it's anhydrous CaCl2 then you could dissolve exactly 0.75g of the dry product to exactly 1.0L in purified water and you then have a reasonable 400mg/l Ca++ std. If it's CaCl2 dihydrate then you could dissolve 1.1g to 1L for the same 400mg/l std.
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