A couple weeks back I had some reef-club friends over, and we tested up a couple salts. Two separate batches of each, all bought within last 3 months from different places, three diff test kits on each sample.
I've got all the excessive data here:
http://www.madisonreef.com/forum/viewtopic.php?t=364
But I do say ...
no matter what my salt tests, test your own. Make it a regular practice with the beginning of every bucket ... it's only one test every few months, and a whole lot of peace of mind IMO.
These results aren't what I got off IO in the past, but as they're all seeming to change packaging regularly ... seems like formulations might be different too.
But here's the quick run-down:
Instant Ocean Batch 1:
1.0265
Calcium Average: 380 [366.7]
Alkalinity Average 12.6 dKh
Magnesium Average: 1380
Strontium: 4
PO4: 0
NO3: 0
Instant Ocean Batch 2:
1.0250
Calcium Average: 367.5 [356.7]
Alkalinity Average 12.53 dKh
Magnesium Average: 1250
Strontium: 10
PO4: 0
NO3: 0
Reef Crystals Batch 1:
1.0266
Calcium Average: 472.5 [451.7]
Alkalinity Average 12.8 dKh
Magnesium Average: 1435
Strontium: 0-3
PO4: 0
NO3: 0
Reef Crystals Batch 2:
1.0262
Calcium Average: 455 [443.3]
Alkalinity Average 12.6 dKh
Magnesium Average: 1400
Strontium: 10
PO4: 0.1 [likely due to unclean bucket/powerhead]
NO3: 0
Tropic Marin Pro Reef Batch 1:
1.0252
Calcium Average: 455 [435]
Alkalinity Average 8.7 dKh
Magnesium Average: 1400
Strontium: 0-3
PO4: 0
NO3: 0
Tropic Marin Pro Reef Batch 2:
1.0259
Calcium Average: 437.5 [421.7]
Alkalinity Average 8 dKh
Magnesium Average: 1300
Strontium: 0-3
PO4: 0
NO3: 0
---
For Calcium average, one test kit was factored out of the average [due to consistent low readings, about 50 points low]. Average of all three listed [in brackets after].
Do note, Strontium test is +/- 5 ... and seemed to be agreed that it's a problematic test. I would not call them conlusive results with this test kit, but that's my editorial opinion.
All salts were mixed using my RO/DI water, around 76 degrees, TDS 0.