Salt Needs it's own thread.

[TCLynx]

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.

[Bob Campbell]

@Eric - This looks like a useful way to figure out the weight of materials so I'd like to understand the math.  But you lost me when you crossed out the numerator and denominators.  I see the match for 1mol of Cl- but the rest does not make sense to me.

I tried to substitute KCL since you provided an answer and got a MM of 22.99 + 39.098 = 62.1 but that's as far as I get.

[Eric Warwick]

It's called dimensional analysis. Basically, write down your units by putting one on the numerator and one on the denominator. So, 2 divided by 2 is one, correct? So, x divided by x is 1. Remember a fraction is just a number or variable (this may make some peoples eyes glaze over, but I hope you're still with me) divided  by another number or variable. So, a mole (mol) is a unit. A mole is also a variable. So, a mole divided by a mole is 1, and since everything times 1=itself your units "cross out". This is so you can check your work. If you have two units that didn't divide by itself then your work is wrong. But if it's one unit, then in the language of chemistry, you've figured out what happens when you react what with what. This is how scientists can see what the mass of Carbon Dioxide is emitted from a smokestack.  If you have anymore questions I'll make a special thread for this. 

Bob Campbell said:

@Eric - This looks like a useful way to figure out the weight of materials so I'd like to understand the math.  But you lost me when you crossed out the numerator and denominators.  I see the match for 1mol of Cl- but the rest does not make sense to me.

I tried to substitute KCL since you provided an answer and got a MM of 22.99 + 39.098 = 62.1 but that's as far as I get.

[TCLynx]

Actually Eric, a thread or perhaps even a whole Group for Chemistry (and the math that goes with it) is probably a really really good idea!

[Eric Warwick]

Making it right now!

TCLynx said:

Actually Eric, a thread or perhaps even a whole Group for Chemistry (and the math that goes with it) is probably a really really good idea!

[Eric Warwick]

For the thread I hijacked--here's the new group: http://aquaponicscommunity.com/group/chemistry-math-and-aquaponics Ask as many questions as possible! Hope you like it!

[Bob Campbell]

@Eric - I see... It's just the units that cancel.  The quantity remains as part if the equation.   Got it

Thanks,