OK, I got the sample from Thomas (Thomas 712) yesterday and tested it today.
Before I give any results, let me be clear about a few things. I can only vouch for things that I did myself. So I will state that the sample that I received has the results and interpretation that I'm giving below to the best of my ability.
But folks should be clear that I am not making any claims about Instant Ocean salt (at least at this point). Without any insult intended to Thomas, I do not know him, and more importantly, I do not know where the sample actually came from. It might be a bad batch of IO. Or it might be something else. Maybe it was adulterated (by him or someone else). It could be just about anything, for any number of reasons. Stuff like that does happen.
OK, with that disclaimer aside, here's what I found:
I tested pH with my just calibrated pH meter. Alkalinity was measured with a Salifert test that I had recently confirmed was approximately correct using alkalinity titrations with a pH meter and commercial standard acid solutions.
I mixed up the salt that Thomas sent in a clear glass jar that had been rinsed with RO/DI water. The water was added to the jar and the conductivity was measured to be about 1 uS/cm. I added the salt and stirred it for a few minutes using the conductivity probe. I kept adding salt until I reached 53 mS/cm (35 ppt). This took about 3-5 minutes. At the end of that time, the solution was fairly clear, with a few solid salt crystals on the bottom.
Interestingly, the water then began to cloud up. It got worse and worse. Eventually if was very cloudy (not quite skim milk, but on its way to that).
I did the exact same thing with a batch of IO that I had bought about 3 weeks ago at a local store. It mixed up clear, and stayed clear.
I measured the alkalinity in my tank water and found 3.3 meq/L (9.2 dKH).
I measured the alkalinity in the fresh IO that I bought and found 3.2 meq/L (9 dKH).
I measured the alkalinity in the salt sent by Thomas (using the cloudy solution without any filtration) and I found a whopping 34 meq/L (95 dKH). Interestingly, the cloudiness went away during the alkalinity titration (as one would expect for a salt like calcium or magnesium carbonate).
I monitored the pH of the solution as it clouded. I do not want to put too much emphasis on exact pH numbers because the precipitating CaCO3 may well have gotton onto the probe tip. Nevertheless, the pH was dropping, from about 8 when mixed to 7.77 to 7.53 to 7.37.
The solution made from IO that I bought did not drop in pH, or cloud up.
I made up an entirely new test solution with the Thomas material, using the jar that I had used for my Instant Ocean. Again, it started clear at about pH 8. I could take the pH probe back and forth between the clear second batch of Thomas material and the older clouded Thomas material, and the pH difference was more than 0.5 units. The second Thomas sample clouded up after about 10 minutes. I've not measured the pH again because I broke the glass tip stirring with the pH probe.
So, my conclusion based on these various observations is that:
1. The material is clearly not similar to IO that I bought myself.
2. The material is clearly unsuitable for use in an aquarium.
3. It is most likely that the material has too much in the way of bicarbonate salts in it (maybe carbonate too).
4. When mixed and allowed to sit for a few minutes, calcium and magnesium carbonate likely precipitate from solution, lowering the pH.
If I had opened a container of IO and got these results, I would be very angry. I would complain to customer service, and point out that a replacement bucket isn't going to make everything better (though it is probably all you will get). I would also point out that they'd better get their act together, or the reputation of IO will be rapidly diminishing as these results are already being discussed on the 40,000 member reefcentral board. (Actually, if it were me, I'd write an article on it, but until more folks find the problem, or it happens to me, I likely won't).
