Mixing saltwater

[hypertech]

What do I need to mix saltwater. I'm going to put my order for dry goods in this week and want to make sure I have everything I need.

Can I just throw the RODI water and salt in a bucket and mix it with a drill paddle?

OR, do I need to by heaters, powerheads, airstones, etc?

How do I go about mixing saltwater?

[Irenicus]

I would get a bucket or a food-grade container (55gal drum, Rubbermade Brute Trash Container) for the mixing. A heater and a submersible pump/powerhead will also be needed. You'll also need a reliable salinity measurement tool if you don't have one already.

[coralreefer]

You definately want to grab a heater and an air pump with an airstone. Powerhead is optional. I would heat and aerate the RO water for 24 hours then add the salt (maybe a fifth to a tenth at a time, making sure to thoroughly mix). If you mix it too fast the water will turn cloudy, from Cl2. Cl2 is much harder to dissolve in water than NaCl and other salts and will be harmful to your tank inhabitants. I have heard some people recommend that you let your mixed seawater sit for a week. This is more helpful for people that house SPS corals and may be overkill for your setup. I usually let it sit three or four days after mixing, however

[hypertech]

Do you run the airstone and/or powerhead during the 3/4 days.

I'm only going to have a 29 gallon tank, so I don't expect to be making mush more than a couple gallons at a time.

So, I will need:

Small heater
Air pump
Air stone
Powerhead/water pump

[morty]

Here is a good article about mixing SW:

http://web.archive.org/web/20001212230600/http://www.animalnetwork.com/fish2/aqfm/1997/sep/bio/default.asp

Towards the end the author mentions the only thing you really have to worry about if you want to use the water right away is low pH due to excess CO2 in the water. An airstone in a medium-sized batch (20gal or so) for an hour would probably take care of it.

I personally am not a fan of letting a batch sit in a plastic container for more than a few hours. Have you ever tasted drinking water that sat overnight in a plastic cup (like a metrodome souvenir cup)? Eww. Tastes like plastic, and I wonder what fish experience when their water has sat for a while in a plastic tub. Doesn't seem to hurt them, but it can't feel natural to them...

[coralreefer]

Do you run the airstone and/or powerhead during the 3/4 days.

Yeah, I would keep it aerated and heated the whole time right up until you do the water change.

[Irenicus]

Do you run the airstone and/or powerhead during the 3/4 days.

I'm only going to have a 29 gallon tank, so I don't expect to be making mush more than a couple gallons at a time.

So, I will need:

Small heater
Air pump
Air stone
Powerhead/water pump

Your going to want something (powerhead/pump) to cirulate the water. I don't use an airstone or air pump and have never had a problem.

I just add the amount of salt (at one time) to get the water to 1.025 and let mix for one or two days before using.

[David Grigor]

Hypertech,

When I had a 58g and would do 6g water change, the procedure was very simple:

1 empty salt bucket with lid ( I used an older 200g salt bucket which is closer to 6g, smaller new bucket will do fine too but slightly smaller ), 1 mj 1200.

That's it. No heater, no airstone.

1.Add R/O water to a premeasured line
2.Put powerhead on in the bottom of the bucket.
3.Add your salt ( again I figured out just how much salt needed to it was an easy repeatable process with only an occasional fine tuning just before using the salt)
4.This is optional but I did add additional CA & MG to match my show tank levels.
5.Put the lid on the bucket ( Not airtight just sit on loosely to prevent most evaporation and to help insulate.
6.Let it sit overnight to allow the powerhead to heat the water.
After 12/24 hours is was ready and the temp of the water was 80 just from the heat of the powerhead. No heater needed. Even in the winter when water is close to 50 and basement temps in 60s the powerhead alone was enough since it was such a small volumne of water.

Note: It has to be a Maxijet 1200. Smaller MJ pumps didn't generate as much heat and the added gph really got the water swirling pretty good so mixed very thorough.

[Chris Goetz]

and as Barry said you will also have to have either a hydrometer(<$10) or a refractometer($35-$100+) to check your specific gravity.

If you want a hydrometer, I probably have an extra I can get you and could check it against my refractometer first so you know far it is off(they usually are off a bit).

If you have the $40 I'd just buy the cheap refractometer from Dirk or DrF&S and skip the hydrometer altogether.

Chris

[David Grigor]

forgot to mention I also used the cheap coralife digital thermeter as a visual check for the temp the next morning.

http://www.premiumaquatics.com/corallife/00232.jpg

And as Chris mentioned, used a refractometer to double check the salinity befure using.

[REEFSTOCK]

Our house is about 70 and we don't bother with a heater unless we are doing a huge change.

Bucket,
maxijet 900

Thats what we use.

[hypoxia]

So how does Chlorine (CL2) wind up in the saltwater batch as it's aging? My tired brain isn't computing. . . . :/

[hypertech]

I've got on my order:

160 gal bucket of reef crystals
Maxijet 1200
portable refractometer
100W stealth heater (for tank)
2 - thermometers (1 for tank 1 for bucket)

From what I'm hearing, that will meet my needs.

Thanks!

[coralreefer]

So how does Chlorine (CL2) wind up in the saltwater batch as it's aging? My tired brain isn't computing. . . . :/

I was just saying that if you dump all the salt that your mixing in at once you will produce more chlorine than if you were to slowly mix it (add small amounts and thoroughly dissolve). I don't think that letting it will result in chlorine. In fact, the reverse is probably more likely (reduction of chlorine) as every element in solution will head towards equilibrium.

[kjdeut]

My rubbermaid for RO/DI water has a heater, airstone and power head. When mixing I add water from the rubbermaid to my bucket, add salt, mix and add to the tank. Not that I am doing it right but I have never let mine sit for any amount of time. I use IO and by the time I mix and carry the bucket up stairs to the tank it is already clear.

Ken

[wkjames]

I was just saying that if you dump all the salt that your mixing in at once you will produce more chlorine than if you were to slowly mix it (add small amounts and thoroughly dissolve). I don't think that letting it will result in chlorine. In fact, the reverse is probably more likely (reduction of chlorine) as every element in solution will head towards equilibrium.

I've been following this thread with great interest. Please explain where the CL2 comes from at all? In the mixing process are we breaking down the salt on a molecular level? What's causing this? It the salt contaminated with free CL2? What does the time passing between mixing and using do to affect CL2 levels?

[David Grigor]

I'm not aware of any chlorine being in salt mixes. Using a RO/DI unit that is functioning properly there will be no chlorine there either.

[hypertech]

I could be way off since I'm new to aquariums and its been a long time since I took chemistry, but here is my guess:

Salt = NaCl (I'm assuming there is some of this in the salt mix but I could be wrong)

When you put it in solution, it becomes Na and Cl ions.

Now, if you over-concentrate the Cl ions, some might combine to Cl2. Chlorine is a very happy molecule as Cl2 so it could be difficult to get it to split and ionize again.

[BiochemRobyn]

Just in case you were curious, saltwater is actually quite a bit more than just plain-old table salt. (So I wouldn't recommend putting table salt in your fish tank if you run out of salt!) Here's the top 7 components of seawater (courtesy of wikipedia and my old oceanography textbook):

Total Molar Composition of Seawater
Water (H2O) 53.6
Chloride (Cl-) 0.546
Sodium (Na+) 0.469
Magnesium (Mg2+) 0.0528
Sulphate (SO42-) 0.0283
Calcium (Ca2+) 0.0103
Potassium (K+) 0.0102

And many other trace elements including bromine and fluorine.

[BiochemRobyn]

Okay, as far as the question of whether Cl- (ionized Chlorine) can form Cl2 (gaseous, reduced form), we can determine whether it is spontaneous by the Gibbs free energy.

The standard reduction potential of chlorine is:
(Cl2 + 2e- = 2Cl-) +1.36 = E

And the equation that we want to use is:
G=-nfE
Where G is gibbs free energy, n is the # of electrons being transferred (in our case 2, but that won't matter because n is always greater than 1), f is a postitive constant (=96,485 Coulombs/mol), and E is the reduction potential.

Any time G is negative, the reaction will be spontaneous. Since in our case, E is positive, n is positive, and f is posibive, G will be negative.

So, this means that chlorine (gas) will spontaneously form dissolved chlorine (Cl-). However, there usually has to be something to catalyze this, so you can't really generalize this to saltwater.

[BiochemRobyn]

opps... repeated the post by accident :smile:

[wkjames]

I was just saying that if you dump all the salt that your mixing in at once you will produce more chlorine than if you were to slowly mix it (add small amounts and thoroughly dissolve). I don't think that letting it will result in chlorine. In fact, the reverse is probably more likely (reduction of chlorine) as every element in solution will head towards equilibrium.

Okay, as far as the question of whether Cl- (ionized Chlorine) can form Cl2 (gaseous, reduced form), we can determine whether it is spontaneous by the Gibbs free energy.

The standard reduction potential of chlorine is:
(Cl2 + 2e- = 2Cl-) +1.36 = E

And the equation that we want to use is:
G=-nfE
Where G is gibbs free energy, n is the # of electrons being transferred (in our case 2, but that won't matter because n is always greater than 1), f is a postitive constant (=96,485 Coulombs/mol), and E is the reduction potential.

Any time G is negative, the reaction will be spontaneous. Since in our case, E is positive, n is positive, and f is posibive, G will be negative.

So, this means that chlorine (gas) will spontaneously form dissolved chlorine (Cl-). However, there usually has to be something to catalyze this, so you can't really generalize this to saltwater.

So per BioChemRobyn, do I properly understand that if I'm using a quality RO/DI filter system producing 0ppm TDS water and a reputable sea-salt product, I can mix and use the saltwater without worry, as long as I don't include chlorine bleach in my recipe???

[David Grigor]

I say yes.

If this were a serious concern. It would have surfaced YEARS ago.

The link that Morty posted about mixing and using the salt in minutes, there would have to be some mention of it if was a serious concern as well as everywhere else.

Better get on the road or you'll be late to the meeting.....I'm leaving now.

[hypertech]

Painful memories ........

I'm gonna stick with $$ + H20 = Reef.

I wish I could go to the meeting. I have to stay home and do homework :(

[hypoxia]

Biochem, that's what I thought. Holy cow, I remembered correctly, and it's been a few years.

The reason I inquired further is that in the last two batches I've whipped up the mix has appeared milky and over-aging has not cleared up the issue. I haven't changed anything about how I prepare, and the water is from the same source (WOF). Come to think of it, I wonder if their RO/DI unit is needing new filters or something.

Testing the tank's water 24, 48, and 72 hours after adding the milky water has not yielded any fluxuations in measurements, and the health of the tank occupants has not suffered in any way.

Anyhoos, I apologize if I've hijacked the thread.

[droinablunt]

when I first set up my 150 filled it with ro water and then in went the whole bucket of reef crystals within a few seconds. cloudy for a few hours and all good since. now for water changes I put ro in a 55 gal with a mag 12 and heater then start pouring in salt (about a 3rd of the bucket) let sit for a hour to heat, check salt level and then it's good to go!

[Soltaker]

Okay, as far as the question of whether Cl- (ionized Chlorine) can form Cl2 (gaseous, reduced form), we can determine whether it is spontaneous by the Gibbs free energy.

The standard reduction potential of chlorine is:
(Cl2 + 2e- = 2Cl-) +1.36 = E

And the equation that we want to use is:
G=-nfE
Where G is gibbs free energy, n is the # of electrons being transferred (in our case 2, but that won't matter because n is always greater than 1), f is a postitive constant (=96,485 Coulombs/mol), and E is the reduction potential.

Any time G is negative, the reaction will be spontaneous. Since in our case, E is positive, n is positive, and f is posibive, G will be negative.

So, this means that chlorine (gas) will spontaneously form dissolved chlorine (Cl-). However, there usually has to be something to catalyze this, so you can't really generalize this to saltwater.

I can honestly say that blood would shoot out of my eyes if I made an effort to comprehend what you just said. :brainoverload:

[BiochemRobyn]

I can honestly say that blood would shoot out of my eyes if I made an effort to comprehend what you just said. :brainoverload:

LOL.... I was forced into learning it :help1:

[Soltaker]

LOL.... I was forced into learning it :help1:

"forced" ? ? ? ? ? :confused:

[mtfatwork]

wow....


you mean you guys mix the salt BEFORE you put it in the tank????




Man have I been doing it wrong.....lol

[BiochemRobyn]

"forced" ? ? ? ? ? :confused:

Unfortunately, you can't graduate from the U in the sciences without physics and chemistry.

[hypertech]

Unfortunately, you can't graduate from the U in the sciences without physics and chemistry.

You can if you take AP Chem in high school. I got 9 credits for that one :beerchug:

[Soltaker]

Unfortunately, you can't graduate from the U in the sciences without physics and chemistry.

ah :cool:

[BiochemRobyn]

You can if you take AP Chem in high school. I got 9 credits for that one :beerchug:
Nice! I went post-secondary, but sometimes I really wish that I had taken more AP courses



ah :cool:
Yeah, I should have explained that comment :idea:

[Soltaker]

Nice! I went post-secondary, but sometimes I really wish that I had taken more AP courses




Yeah, I should have explained that comment :idea:

It's all good! :tongue1:

[Kenny Graham]

:swear: What, they had chemistry in college. I took :beerchug: instead.