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I don't usually track salt levels, however, if you were to salt your system for some reason, over time if you do water changes or as salt gets used by the plants, you may have no idea what the salt level is later if you for some reason needed to salt again.
Primary reasons for salting are to do with fish health. 1 ppt of salt can help mitigate nitrite poisoning if there is a nitrite spike while there are fish in the system. 2-3ppt of salt can be a nice general tonic for the fish, helping sooth their skin and promote a good slime coat and help them balance osmotic pressure and so on. A sudden shift (3 ppt change) of salinity can help battle certain parasites like ich and other diseases can be battled by salt.

Salt can also be used as a bath or dip for injured or ill fish.

However, one must do their research into the salt levels that are appropriate for different kinds of fish. From my recollection Blue Gill and Channel Catfish can only handle salt up to 5 ppt. After seeing how my fish reacted to salt between 4 and 6 ppt, I decided 3 ppt was plenty for the channel catfish so I usually keep it below that. Tilapia can handle lots more salt, there is a population of Blue Tilapia that have naturalized in Tampa Bay off the Gulf of Mexico.

Salt can also provide some trace elements.

I usually recommend solar pool salt or solar water softener salt. It is generally the cheapest stuff with no special additives and is simply solar dried sea water.

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Well it seems like a good presumption Bob...Perhaps an expensive and un-necessary one, but still... I imagine that you'll get most of that stuff and then some from MaxiCrop, Seasol or Kelpak...or probably any product that is a cold extraction kelp based. My belief is that plain old sea water would be the ultimate 'trace element' "product" to use in an AP system...(granted with the way that we are treating our Oceans these days, I may have to change my tune)...

Now, I have no friggin idea how a fishes slime coat (glycocalyx) is effected by different salts or the mechanisms by which it forms/regenerates...as it stands for now, in my mind it's hygroscopic-osmotic-fishy-voodoo magic. But, I do know that the Chloride ions (in NaCl or any other chloride salt) is what you'd be after when mitigating nitrite toxicity (brown blood disease) in the fish. I linked a study that explains it well (and thankfully short/quickly) in the "Documentaries, links and books" thread/group...

Briefly, the chloride ions, through a mechanism called competitive inhibition, will limit the ability of of nitrite uptake by the fish...by "taking up the places" on the gills where the nitrite normally would go, keeping much of it out of the blood...but that's another story I guess...not slime coat...

The Mg, Ca, K, and Na in that product come in the form of chloride salts...

Those other essential elements you should already have in your system, if you're feeding your fish a normal healthy diet, and/or are using MaxiCrop or whatever because your system is brand new, alternating buffering regime etc...and if it turns out the chloride is what the slime coat needs, well...pool salt is probably a good deal cheaper than that product, I'm guessing. Or, if you are adjusting the pH of your top up water with HCL you would certainly be adding chloride ions there, as the HCL and carbonates neutralize one another...

There are a number of studies that are showing that Na may take up the functions of K in plants (and the human body) to an good extent, so I wouldn't really sweat it on the plant end at a couple of ppt...(strawberries notwithstanding apparently).

Just my 2cents... 

http://cdn.arbico-organics.com/downloads/maxicrop-kelp-analysis.pdf   trace element analysis of MaxiCrop...

http://www.scribd.com/doc/28844195/Nutrient-Cycle-and-Sludge-Produc...  analysis of what you tilapia are shitting  out into your water over time (may vary with diet of coarse)...



Bob Campbell said:

I've been keeping 0.15% water softener salt in my pond for many years.  The plants don't seem to mind, but I'm growing a variety of vegetables in my aquaponic systems, and wonder if there are other salts besides sodium chloride that would help keep the fish slimy and benefit the plants at the same time rather than stress them.

I'm getting from what has previously been posted here that 0.15% sodium chloride is not enough to harm most vegetables, but I'm wondering if Ca2+, Mg2+,. Zn2+ and  FE2+ might not provide enough irritant to the fish to promote slime and benefit the plants at the same time and allow for less sodium chloride to be kept in the water.

Hay Vlad, I know of people who do get some sea water to use in their systems on regular basis.  Granted this is only appropriate for people near the sea since shipping sea water would be a bit ridiculous.  And my understanding is that the sea water or Sea 90 salt have pretty much the same elements as found in the seaweed extract but please don't quote me on that since I haven't had time to double check that.

It's good to know that using potassium chloride would be appropriate for mitigating nitrite since that is pretty easy to get in bulk of course it would probably mean new math equations to figure out how much to use to get to an appropriate level and I have no idea how one would go about measuring it.

Yeah if I lived by the Ocean, (or by some old salt flats) I'd sure use it...

Well now, young Eric Warwick, or Nate would be much more qualified than I to do such calculations but the skinny of it would be:

Calculate the molecular mass (MM): 
MM = 22.99 + 35.45 = 58.44

Calculate the total mass of Na present: 
1 Na is present in the formula, mass = 22.99

Calculate the percent by weight of Na in NaCl: 
%Na = (mass Na ÷ MM) x 100 = (22.99 ÷ 58.44) x 100 = 39.34%

Calculate the total mass of Cl present: 
1 Cl is present in the formula, mass = 35.45

Calculate the percent by weight of Cl in NaCl: 
%Cl = (mass Cl ÷ MM) x 100 = (35.45 ÷ 58.44) x 100 = 60.66%


You can use this crap for whatever compounds...you just have to know (look up) the atomic weights of those elements...


So say, by weight salt (NaCl) is about 61% Cl...being hygroscopic, it may pick up some water weight, but I'm not about to go there...

For potassium chloride this would work out to be about 47% Cl...

Yea, I tend to depend on people like Rupert or Nate, or yourself to help me with the chemistry.  While I'm actually quite good at math oddly enough, my dyslexic self never made it though chemistry (the prof never taught how one was supposed to figure out the formula or equations so it seems that to do chemistry one had to memorize it all rather than following rules the way ya could for math.  Being dyslexic I don't memorize formula visually since they would all be jumbled all the time so I gave up.  I expect that with a different teacher I might have gotten it because I know there have to be rules to how you figure it all out.

I somehow just found this thread (stalking Vlad), and I thought I'd throw in a recent discovery. I salted my Sac Perch tank, which is also my duckweed tank, at 5ppt, and the duckweed is growing fine. I was worried it would slow or stunt, but no problem for 3 weeks now.

That's what's nice about any community eh? Everyone seems to have their own "piece of the puzzle". Yeah, I bet with a different teacher, things would've been quite different. ..I still thank some of mine in my head, throughout the day...what a difference they can make...



TCLynx said:

Hay Vlad, I know of people who do get some sea water to use in their systems on regular basis.  Granted this is only appropriate for people near the sea since shipping sea water would be a bit ridiculous.  And my understanding is that the sea water or Sea 90 salt have pretty much the same elements as found in the seaweed extract but please don't quote me on that since I haven't had time to double check that.

 

I'm one of them... and have been doing so in my AP systems since day one...

 

I also used to formulate my own hydro nutrients... and often added a proportion of seawater as a base...

 

Likewise on my soil gardens... especially when they were "fallow"...

 

Seawater is the most concentrated form of trace elements available... and probably more so than most seaweed/kelp extracts...

And then there is human blood...mwuuuhahaahaahaa....just kidding. There aren't enough virgins around here for that to work...

Hehe. Sounds like those Transylvanian women need chastity belts AND steel neck guards. :)
Hey smart people. Is there a way to remove only the sodium from seawater?

Vlad, the mass will be different for Cl- and Na+, but they are in a one to one ratio. What you would do is a little more complicated. You'd need to find the number of atoms, dunh, duhn, duhn.* A mole (not the fuzzy brown creature that eats our wonderful plants) is:

6.02X10^23 or 6.02E23 atoms

So, since NaCl is a 1 to 1 (1:1) ratio you need to find only one element (or two if you need to check your work). 

Here's how to set up the problem: 1g of NaCl X 1mol of NaCl X    1mol of Cl-    X  6.02E23 atoms = atoms of Cl-

                                                                       1               58g of NaCl       2mol of NaCl        1mol of Cl-


(Substances are in bold; mol=mole; g=grams) 

For those of you who this might be a horrible mess of math remember that if you write down your units you can do anything. Remember like units cross out if one unit is the numerator (on the top) and the other is a denominator (on the bottom). So, once you've neutralized your units you can cross them out, like this: 

 1g of NaCl X 1mol of NaCl X    1mol of Cl-    X  6.02E23 atoms = atoms of Cl-

           1              58g of NaCl       2mol of NaCl        1mol of Cl-

See, it leaves you with atoms of Cl-!

What is left to do to calculate you ask? Well, multiply the top row, then divide by the bottom row after it was multiplied together. Or,  (1X1X1X6.02E23) Or 6.02E23 divided by 116. There that's the number of atoms. 

                              (1X58X2X1) 

Then you'd translate that into the molar mass--then put it in mg/liter and that's ppm so ppt would be .0003mg/liter. 

*Or, as I just realized, you'd convert molar mass to grams and do mg/liter. (I wrote out this whole explanation of chemistry math, so I figure I should just post it--you could go to the number of atoms to check your work as I said above.) 

Post Script: TCLynx I hope this helped rather than confuse you.

Vlad Jovanovic said:

Yeah if I lived by the Ocean, (or by some old salt flats) I'd sure use it...

Calculate the molecular mass (MM): 
MM = 22.99 + 35.45 = 58.44

Calculate the total mass of Na present: 
1 Na is present in the formula, mass = 22.99

Calculate the percent by weight of Na in NaCl: 
%Na = (mass Na ÷ MM) x 100 = (22.99 ÷ 58.44) x 100 = 39.34%

Calculate the total mass of Cl present: 
1 Cl is present in the formula, mass = 35.45

Calculate the percent by weight of Cl in NaCl: 
%Cl = (mass Cl ÷ MM) x 100 = (35.45 ÷ 58.44) x 100 = 60.66%


You can use this crap for whatever compounds...you just have to know (look up) the atomic weights of those elements...


So say, by weight salt (NaCl) is about 61% Cl...being hygroscopic, it may pick up some water weight, but I'm not about to go there...

For potassium chloride this would work out to be about 47% Cl...

Dear God good man, I think you've gone too far!

As fun as counting atoms might be...I think that percentage of weight might be much less intimidating for folks. And still hopefully get you close enough for hand grenades and backyard AP....

See, TC already knows how much sodium chloride to add to add (by weight and/or then volume) to get her to 1ppt and if she knows (by weight) what percent of the sodium chloride in her 5 gallon bucket (yeah, a couple atoms might slip by un accounted for with the bucket and bathroom scale method) is chloride, then she could roughly do the same (by weight) for potassium chloride, knowing what percent (again by weight) is chloride and what percent is potassium.

I know this would not fly in a Krebs cycle application or whatever...But hopefully percent by weight to ppm (or mg/L) should be 'doable' by most people...

Say you want to add some Mg to your system...

If you know that magnesium sulfate (MgSO4) in the form of Epsom salt (MgSO4-7H20) is roughly 10% Magnesium, (by weight) it would appear to make things pretty easy...

Knowing this, and knowing your target threshold amount (in mg/L or ppm or whatever you choose to call it) and knowing your total system water volume...it should be easy to calculate how much Epsom salt to use...Say, my particular teaspoon holds about 3 grams according to my gram scale. But you should measure yours...and you add one teaspoon (3 grams) of Epsom salt to 1 litre of water... only 10% of those 3 grams is actually Magnesium...So 300 miligrams of Magnesium. You can see where this is going, right...?

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