How do I know if my test kit is accurate? Well, I might have found the answer!

The hard part:
First, you have to make sure that your refractometer is calibrated. Either make your own salinity from a proven recepi, or purchase Marine pinpoints calibration fluid. You cannot use any other brand and also, RO water is not accurate.

The easy part:
mix your salt sample to 35 or 1.026

"Here is a list of what I measured for the big three in a number of the salt mixes we use today. This is intended as a guideline and I, in no way, guarantee these figures. All I can say is they were all tested under the same conditions, with a number of different brand test kits, using the same methods for each test. I believe these numbers are reasonably what you can expect from these salts mixed at 35 ppt or 1.0264

A special thanks to Bertoni for putting it in nice form."

Calcium Alkalinity Magnesium
Aquatic Gardens 430 8 1240
CoraLife 560 9 1380
Instant Ocean 350 12 1070
Kent 540 11 1200
Oceanic 580 8.5 1650
OceanPure 510 10 1320
Red Sea 400 8 1300
Red Sea Coral Pro 490 7 1300
Reef Crystals 420 12 1260
SeaChem Marine Salt500 10 1400
SeaChem Reef Salt 540 10 1450
Tropic Marin 375 10 1230
Tropic Marin Pro Reef 450 8.5 1380

I figure I'd try a few kits and see where they shake out a bit. So here are my results:

TMPR= 450/8.5/1380

Calcium
Elos: 425
API: 500
Salifert: 425

Magnesium:
Salifert: 1200

ALk:
API: 8.0

Salt mixes seem to vary and I don't think are any more reliable than the test kit used on it. Just my opinion though.

Salt mixes seem to vary and I don't think are any more reliable than the test kit used on it. Just my opinion though.

I agree that salt invariably will probably vary, however, it could give you another "big clue" to check your test kit to see if it's way off on the "big 3" Calcium, Alk, & Mag. IMHO.
on a side note, I think it's strange that Elos & Salifert matched TMPR at 425, yet my tank water Elos was 425 and Salifert was 480. Also, API was 500 on the TMPR yet, 520 on my tank water.

But I feel very confident (after doing this) about my API KH, and my Elos Calcium. This was cheap & easy.

Sounds complicated to me. Why not just enjoy your tanks and spend less time testing the water? :)

I test when something looks off or occasionally when Danny comes. I have been testing more frequently lately as I add a Nilsen and Calcium Reactor so worried Alk will shoot through the roof.

Sounds complicated to me. Why not just enjoy your tanks and spend less time testing the water? :)

I am testing & posting results to help out members so that the next time they have some issues going on in their tank, they can grab a certain kit and be confident that the parameter was the cause or not.

You're right, when things are going well, just sit back & enjoy the tank! However, when things aren't going so well, and your test results are way off causing you to go in the wrong direction (making things worse), it might be nice to go somewhere to validate those results.

I'll give you a brief example:
back in August, my sps were doing horrible. Tips were losing tissue slowly (over a 2-3 month period). I already have a fuge, use phosar, etc. I also, just upgraded my Tunze a few months before. Well my Salifert Alk was showing 9.9, but a lot of people were saying it was my alk and that Salifert was screwed up. Don't trust it. Anyway, to make a very long story short, I talked with the owner Habib, and he agreed that my test kit WAS screwed up. The whole time though it WAS phosphates!
On 1 day of testing the same sample ALK I had:

Salifert(old kit): 10.9
New Salifert kit (from Habib w reference): 13.8
IO kit: 9.9


I think I can also speak for Cameron, too......We are just trying to pass along information that might be helpful to someone at sometime in their reefing.