Salt study

[ccCapt]

AquariumWaterTesting.com did a test on a bunch of the most popular salts used. Here are the results of the study. It's sort of hard to decipher. I use Red Sea Coral Pro and I think those results look good.

There is a thread on RC about it here.

[Kurt_Nelson]

As noted on the RC thread, it's really a shame that they didn't mix up the samples so they all had the same salinity. I can't fathom why they didn't... you can't really use the results directly without scaling them to NSW salinity levels.

Thanks for the link though! Good info to have. (Looks like the "bad batch" of RC was still out there when the test was done. Think I'll just sit tight on my "good bucket" and wait a while to order another one!)

[fijiwigi]

Wow very interesting and I thought my salt was Nitrate and phospate free. If I read the link correctly all of the salts have trace amounts of the bad stuff. The thread on ReefCentral talks highly of the Coralife salt. I debated that salt in the beginning but decided to go with reefcrystals because it seemed to be the favorite.

[Kurt_Nelson]

It's always a good idea to test your new salt water from time to time, just as you'd test your tank water. "Nitrate-free" is a somewhat relative term, I think. Kind of like "fat-free foods". It's "fat-free" and can list on the label "0 g fat" as long as it has less than 0.5g of fat per serving. Nobody says what the serving size needs to be!

[cmor1701d]

Great study, BUT the graphs are meaningless. The SG was different for every brand. They mixed 7g per 200ml RODI water. They did not mix to 35ppt SG so the comparisons can not be made unless you extrapolate numbers for each test of each salt at 35ppt.

[PC]

"...As noted on the RC thread, it's really a shame that they didn't mix up the samples so they all had the same salinity. I can't fathom why they didn't..." / "...They did not mix to 35ppt SG..." You are mixing terminology. Mixing to a SG and testing was not the point of the test. The goal was to measure the amount of elements, believed important to us aquarists, in a given, quantified amount of mix.

"For example, 35 ppt value simply means 35 parts per thousand. If you broke down the water into all it's parts, out of a thousand of those parts, 35 would be salt (sodium chloride). Another way to think of it is simply 3.5%.

The 1.026 sg value is a little trickier. The sg stands for Specific Gravity. Specific gravity is not so much a measure in units, as it is a measure of density as compared against pure water. Pure water has a Specific Gravity (density) of 1.0. SG is a quick way to guestimate the salt content of your water. It is not always the most accurate way, however.
In practice, either value is intended to give you a measure of the concentration of the salt content of the water.
One common mistake made early on, is not taking into consideration the affect temperature has on salinity. Since temperature will make the water expand/contract, as a result, this will affect the density of the saltwater. There is a decent chart that can be found here, which will show the changes in salinity due to temperature." ( The Reef Tank - Powered by vBulletin ) If you consider the goal, which is to compare how much of each element is found in a given, standard sample, than you can conclude that mixing to a given SG is not productive as mixing to an unquantified sg will skew the amount of elements found in any given sample. The quote, however, does raise a *very* important point regarding temperature, which I do not see stated anywhere in the PDF. I do not know that temp would affect the element measurements, but it would have been nice to notate.

HTH, Enjoy!

[melosu58]

Thanks for the info. Very informative.

[cmor1701d]

Most of us mix to an ATC-refractomer reading of 35ppt. It is at this level that we test for water parameters. Knowing that x grams of mix mixes to a y ppt of salinity tells you how much mix of each brand you need. In other words, does a 200 gallon bucket actually make 200 gallons of salt water mixed to 35 ppt using a temperature compensating refractometer.

I then want to compare the amount of trace elements in a sample of salt mixed to NSW (35ppt). That is what the goal of the test should have been. This test did not accomplish that.

[Kurt_Nelson]

Originally Posted by cmor1701d

Most of us mix to an ATC-refractomer reading of 35ppt. It is at this level that we test for water parameters. Knowing that x grams of mix mixes to a y ppt of salinity tells you how much mix of each brand you need. In other words, does a 200 gallon bucket actually make 200 gallons of salt water mixed to 35 ppt using a temperature compensating refractometer.

I then want to compare the amount of trace elements in a sample of salt mixed to NSW (35ppt). That is what the goal of the test should have been. This test did not accomplish that.

Yeah... what he said!

But in reality, the test did accomplish that. You just have to get out the calculator and scale the numbers yourself. They should be linear.

[cmor1701d]

Kurt,

I agree, but the charts and graphs should have been scaled for that. Otherwise you can't really compare one salt to another the way we would use it. To show a chart for conductivity of 7 grams of mix in 200 ml of water and compare it to NSW is meaningless. To prepare the samples to 35 ppt salinity and then compare it to NSW would be meaningful.

If I had the time I would make the calculations and post new charts. New job starts tomorrow so I won't have the time. At least I have a starting point which something I didn't have before this study.