Chemical accuracy of synthetic salt mixes to NSW

[LeeMc]

I would like to ask Randy what his take is on the plethora of salt mixes on the market with their ability to accurately reproduce NSW chemically. Aquacraft.net boasts the existence of an independent lab analysis of these products known as the "S-15" report, and then contrasts this report to their product line. Perhaps a sub-issue is how crucial is it to reproduce NSW chemically, i.e. equivalent molar concentration of elements, in order to have a "healthy" chemically balanced system. If the S-15 report is accurate as of the time it was run, and the salt products have not changed production methods or chemical composition (unlikely) since the report then it certainly raises questions about the quality of salt mixes in contrast to the claims advanced by its makers especially since it appears that none of the salt mix makers advanced any scientifically supported arguments to rebut the report.

Thanks

[Randy Holmes-Farley]

Next Month's article is all about salt mixes, salinity, etc for beginners (first in a multi article series). Here's a segment from that article that addresses this question. Note that I don't even mention the S-15. Partly that is because it is not actually all together in a single place that I can find,and part is that totally bogus scoring system they use. That said, the same issues apply to it as well as the better studies reported below:



Artificial Seawater: Chemical Analysis of Mixes

There are several studies that look at the chemical constituents of salt mixes. Some of these are linked below for those who want to pursue them.

The Composition Of Several Synthetic Seawater Mixes
http://web.archive.org/web/20001215070800/http://www.animalnetwork.com/fish2/aqfm/1999/mar/features/1/default.asp

A Chemical Analysis of Select Trace Elements in Synthetic Sea Salts and Natural Seawater
http://www.advancedaquarist.com/issues/sept2004/feature.htm

Inland Reef Aquaria Salt Study, Part I
http://www.advancedaquarist.com/2005/11/aafeature1

Inland Reef Aquaria Salt Study Part II
http://www.advancedaquarist.com/2005/12/aafeature1


The problem with using such studies to select a salt mix is that while one can look to see which brands most closely match natural seawater, the problem is that none really do, and it becomes very difficult to decide what is best. For example, is it better to have too much sulfate or too little fluoride? Too much borate or too little bromide? Too much strontium or too little potassium? No one knows. Ask that question about nearly every chemical constituent, and the true answer is “no one knows”.

Even worse, salt mixes change formulations and bulk material suppliers periodically, and so the properties change. Even if a salt study analyzes so many samples that it accurately reflects all of the batches of a single salt brand on the market at a given time, a few months later it may be of little value. Several manufacturers, for example, have publicly stated that they have changed their formulation since some of the studies linked above came out.

There are some obvious chemical differences between salt mixes that aquarists readily discover for themselves. These generally relate to the readily measured attributes of calcium, alkalinity, and magnesium. Even here, it is not simple to decide what is best because aquarists often intentionally keep water parameters different than natural seawater (for example, maintaining higher alkalinity than in the ocean), or might want the mix to have an overabundance of something to offset losses in the aquarium (magnesium, for example). Bear in mind that all of these, and most especially alkalinity, are almost immediately altered in reef aquaria by the supplementing that is necessary, and that the exact values in the salt mix may not be of particular importance. They are also easily adjusted by aquarists if they want to do so.


So, despite the fact that I am a chemist and have made many of these types of measurements myself, I don’t think that one should put too much emphasis on such chemical studies. Perhaps toss out of contention those that seem seriously flawed, but that leaves many of them. Better salt mix decisions might be made using the types of information described later in this article.

[LeeMc]

Looking forward to its reading...
Thanks for the feedback

[Randy Holmes-Farley]

You're welcome.

Happy Reefing. :)

[LeeMc]

OK Randy - I confess my desire for immediate gratification....only because I have reached a point where I am ready to make my own Synthetic Sea Water (SSW) to cycle a 225g system. I've read the materials via the links above and conclude that absent a legal regualtion or voluntary complicance to a know standard SSW will constantly be changing compositions for economic/profit and/or manufactuering process. Oddly, I was surprised that "Catalina water" processed locally here in Long Beach, CA. off the coast using NSW contained high levels from samples taken a few miles north in Malibu. A more accurate sample would be to analyze NSW from Figi or the Indio Pacific since that is a better relfection of the NSW our coral critters exist.

Coral physiology seems to be evolving with much of its organic chemistry/physiology still to be discovered. The bottom line appears to be how does an abnormally high (pick your element), say bromine, affect coral and fish physiology? I suspect the LD50 of of many of the high levels of elements in SSW is unknown. You can suppliment a SSW low in elements but you cannot easily dilute high levels. Have you any links to the physiology issue? Maybe the real question is what SSW mix would an educated chemist or physiologist use after studying the data?

[Randy Holmes-Farley]

Another problem with chemical analyses is that it says nothing about the form the chemical takes and how bioavailable it might be. Iron oxide vs soluble iron. One cannot simply look at a chemical concentration assay to know how beneficial or toxic any particular level of a heavy metal might be.


I choose to use Instant Ocean because of its long track record of success, and that what I recommend in the article, along with some others that also have good track records. I just think that there are too many different organisms with different concerns from various ions to pick one based on the chemistry. I also dislike the bioassays out there (Ron's and Eric's).

Here's another section on selecting one:


Artificial Seawater: Real Aquariums and Salt Mixes

So if we cannot rely exclusively on chemical and biological testing of salt mixes as a guide to selection, what can we use? Well, one can obviously look to see what other reef aquarists are using. But, of course, you’d want to select mixes that have resulted in success. Unfortunately, a “poll” of aquarists may simply reflect what is used, not what folks are successful with. It may also have a lot of votes in it by aquarists that have not yet had the aquarium long enough to deem it a success.

Here’s a related suggestion. I looked through the past 5 years of Reef Central Tanks of the Month and recorded what salt mixes were used. So, where's what I found (Table 1):


Table 1. Salt mixes used in the past 5 years of Reef Central Tanks of the Month.
Salt Mix Number of Examples
Unidentified >30
Instant Ocean 9
Reef Crystals 7
Tropic Marin 5
Tropic Marin Pro 2
Oceanic 2
Red Sea 2
Coralife 1
Catalina Water Company 1
Seachem 1
Sera 1
Preis 1


I propose that the exact numbers and ranking are not too important as they reflect aquarist choices as opposed to the “betterness” of salt mixes. However, any mix used in any TOTM shows that one can have a wonderful aquarium using them. Further, picking one of the more commonly encountered mixes in Table 1 may be prudent, since more than one aquarist has shown that a beautiful and successful aquarium can be attained using one of them. So my suggestion is to pick one of the top half dozen mixes above, and then don’t spend any more time worrying about whether your mix is the “best” one or not. Personally, I have used Instant Ocean for more than ten years, largely because it has had a long and wide track record of success.

[LeeMc]

good enough fer me... Looking forward to the series. Thx..

[Randy Holmes-Farley]

:thumbsup:

A couple of weeks.

Happy reefing. :)