Source Water: Choosing Your Salt Mix

Tenji

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Tenji is pleased to present a series of exclusive articles for Reef2Reef members. We will be delving into the various aspects of reef keeping, focusing on tried and true methods that can be implemented by aquarists of all levels.
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Our first installments will be concentrating on the most basic aspect that is frequently overlooked; your source water.

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Once you are producing 0 TDS water from your RO/DI system it’s time to create the ideal reef water by mixing in a synthetic salt. I’m a firm believer you can be successful using any quality salt mix. Very few large salt producers have recurring contaminant issues, so once you find one you like that mixes to the appropriate parameters we recommend you stick with it.

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All salt mixes contain the same base component, sodium chloride, or NaCl. There are only two major suppliers of NaCl in the United States, meaning all of the major salt companies pull from just two sources. We start to see what sets them apart when it comes to the remaining components of a synthetic salt mix, beginning with the magnesium sulfate, or MgSO4. There are various grades of magnesium sulfate available to salt manufacturers ranging from US Pharmaceutical grade to agricultural grade, which is indicative of purity. Many lower purity magnesium sulfate crystals contain anti-caking agents which we wind up seeing stuck all over the inside of our mixing barrels. The jury is still out whether this is detrimental to aquaria long-term, but overall most agree while this is unsightly, it has no direct negative effect. Then major and minor trace elements are added, and as you can probably guess, like magnesium sulfate they are offered in various grades. Cost for the different classifications directly correlates to the price of our salt. Generally speaking, the higher priced salts use purer components. Some companies go even further by solubilizing components to further filter contaminants, which is why we see some salts coming in multiple parts that include liquids.

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Ultimately most quality salt choices are pretty similar, so the next thing to consider is your target parameter range. If you intend to keep alkalinity at 7 dKH you should search for a synthetic salt that mixes close to 7 dKH. Using a salt that mixes to 10 dKH would inevitably stress your animals in your display running at 7 dKH every time you do a water change. The same can be said regarding other elements; if your target calcium level is 350 ppm avoid a salt that mixes to 450 ppm.

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Next thing to consider is availability and cost. If you live in New York, you don’t want to source a salt that’s commonly used in Los Angeles but rarely seen on the east coast. Most local fish stores competitively price salt making them a great place to search for your favorite mix and avoid the cost of shipping a box of minerals across the country. Try to resist the urge of being an early adopter of the next greatest salt mix on the market. New mixes might have supply or consistency issues early on forcing you to change salts.

Ideally, you have a mixing container large enough to dump your entire package of salt mix in. Many of us won’t have that pleasure, so break out the measuring cups! If you are not using an entire package you should thoroughly mix up the contents prior to use. Those dry components we looked at earlier have diverse particle sizes causing some of them to settle out during shipment. It’s very possible to find varying parameters out of the same package if not blended prior to use.

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Once your RO/DI water has filled your mixing reservoir it’s time to heat it up. Salt mixes faster and thoroughly at temperatures above 70°F (21°C). Along with a heater, a decent size powerhead or submersible pump will dissolve the salt mix post haste. Don’t skimp on the pump or you might wind up spending additional time helping the salt dissolve. Find a pump that will keep the surface of the water churning. Some salt manufacturers recommend mixing for 24 hours, however, there are now several options that can be used in as little as fifteen minutes. Keeping your reservoir full of ready to use saltwater can save your system in an emergency. Having a 100% water change handy is ideal, although aiming for 50% total system volume would be a more realistic goal. If you intend to store saltwater long-term we recommend you keep it lightly aerated with a pump to prevent elements from precipitating out of solution.

That wraps our take on source water, in our next article we’ll start discussing the fun stuff… equipment!
 
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revhtree

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Thank you for the great info!
 

cracker

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I'm using 2 different salt with 2 different systems. I use one for the big 180 to save a little$$ & it has a higher alk . The other costs more but the Alk is lower & matches what I want.
Great article stated in simple terms.
 

hart24601

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Very nice, I do have a couple points I am curious about.

"Generally speaking, the higher priced salts use purer components."

I am not sure about the higher cost always meaning the reagents are higher grade. I know a couple high end salts use high grade materials, but do we have evidence the more inexpensive salts do not use the same purity like Instant Ocean, Aquaforest and Fritz using lower quality materials (I think those are less expensive) than ESV, TM, KZ or HW?

I also think it would be good to show an example of the impact on alk of doing a WC with a salt mix that is higher alk than the display as generally it doesn't make a very large impact. Say 7.5dkh display and 9dkh salt mix if doing a 10 or 20% waterchange. If doing AWC then the higher alk and calcium might be a benefit as you add them dosing anyway. I don't think a higher alk matters much for W/C unless doing very large ones.

Still nice article! Just my initial thoughts.
 
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Tenji

Tenji

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"Generally speaking, the higher priced salts use purer components."

I am not sure about the higher cost always meaning the reagents are higher grade.
Hence "generally speaking" ;)
I know a couple high end salts use high grade materials, but do we have evidence the more inexpensive salts do not use the same purity like Instant Ocean, Aquaforest and Fritz using lower quality materials (I think those are less expensive) than ESV, TM, KZ or HW?
A simple means of identifying component purity (namely magnesium) is the build-up of elements within the mixing vessel. If we note anti-caking agents precipitating out of solution, it is safe to assume they skimped on other components as well.

I also think it would be good to show an example of the impact on alk of doing a WC with a salt mix that is higher alk than the display as generally it doesn't make a very large impact. Say 7.5dkh display and 9dkh salt mix if doing a 10 or 20% waterchange. If doing AWC then the higher alk and calcium might be a benefit as you add them dosing anyway. I don't think a higher alk matters much for W/C unless doing very large ones.
Correct, if only thinking in terms of 10-20% water changes you won't likely see much of a shift. Although since our goal is to keep parameters as stable as possible, why allow for any shift?

If you fall behind on maintenance, have a nutrient spike, or an emergency situation, you'll be considering significantly larger water changes. No hobbyists should be afraid of doing 40%+ water changes, even if just once a year to flush out contaminants. There's more detail on this in this MACNA presentation if interested.
 
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How many of us actually mix up a new bag or bucket of salt? I haven't in a long time.
For those who do please share your method with us.
 

Dom

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Thank you for taking the time to write this; great information!

One point I'd like to make...

The article states:

"Having a 100% water change handy is ideal, although aiming for 50% total system volume would be a more realistic goal."

I have read in posts here on R2R that once mixed, water should be used within a day or two as long term storage of mixed water suffers from breakdown and can be detrimental to your tank.

Is it safe to store mixed water or not?
 

IronDruid

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Thank you for taking the time to write this; great information!

One point I'd like to make...

The article states:

"Having a 100% water change handy is ideal, although aiming for 50% total system volume would be a more realistic goal."

I have read in posts here on R2R that once mixed, water should be used within a day or two as long term storage of mixed water suffers from breakdown and can be detrimental to your tank.

Is it safe to store mixed water or not?
As long as the water isn't evaporating and the container isn't leaching anything I can't imagine why a saltwater mixture would go bad. Then again I'm new to the hobby and still waiting on my tank so what's my imagination worth lol

Will probably have to check to make sure nothing's settled on the bottom though :)
 

pdiehm

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The most interesting thing was heating the water up prior to mixing salt. I use the Red Sea blue bucket, and they strongly recommend colder is better, and also recommend not letting the mixed saltwater sit.

I have asked them about mixing the bucket of salt up prior to use and was advised that it makes no difference (I do it anyhow out of force of habit).
 
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Tenji

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I have read in posts here on R2R that once mixed, water should be used within a day or two as long term storage of mixed water suffers from breakdown and can be detrimental to your tank.

Is it safe to store mixed water or not?
Certain elements can precipitate out of solution from some mixes, however, most do not. We recommend following manufacturer recommendations if they state to use it within "X" amount of time. We do not use any mixes where this happens so we're able to keep ready-to-use saltwater on hand at all times.
The most interesting thing was heating the water up prior to mixing salt. I use the Red Sea blue bucket, and they strongly recommend colder is better, and also recommend not letting the mixed saltwater sit.
We have never seen them recommend "colder is better". I found this pdf online regarding Red Sea Pro (black bucket) which states "Use reverse osmosis (RO) water at approximately 20°C/68°F. Always add the salt to the water... Raise the water temp to 25°C/77°F and measure the s.g./ salinity with an accurate hydrometer/ refractometer. Add salt or water as necessary to achieve the desired parameters." I assume this is the minimum recommended mixing temp which would save you some electricity. Would love to know more if they're stating something elsewhere!
I have asked them about mixing the bucket of salt up prior to use and was advised that it makes no difference (I do it anyhow out of force of habit).
Red Sea brand might be the exception to this tip since it is dehydrated seawater, rather than a concoction of ingredients sourced from different areas. With that said they still add ingredients which could settle out, so we would still recommend thoroughly mixing prior to solubilizing.
 
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Tenji

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So the salinity would be different at 68 than 77?
Correct.

"Temperature and density share an inverse relationship. As temperature increases, the space between water molecules increases—also known as density, which therefore decreases. If the temperature of water decreases its density increases, but only to a point. At a temperature of 4°C pure water reaches its maximum or peak density, cooled further it expands and becomes less dense than the surrounding water which is why when water freezes at 0°C it floats.

Salinity and density share a positive relationship. As density increases, the amount of salts in the water—also known as salinity, increases. Various events can contribute to change in the density of seawater.
" Source

This is why you'll see some refractometers note "ATC" (auto temperature compensation), meaning they will automatically compensate for different temperatures within a given range.
 

pdiehm

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Oh ok. My refractometer is an atc. Will check salinity at cold temp and at tank temp next time.
 

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