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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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Some plants do fine with salt levels and others will suffer if you bring the salt level up too high.

for example
Strawberries are sensitive to salt.
Tomatoes can take quite a lot of salt.
Where have you found the best information on fish phsyiology, such as salt tolerances?

Thanks,
David
Truth is I've generally just done a search on the internet then sift through some of the information. There is lots of info about most common species, especially ones that are farm raised or common game fish.
My system is about 2 mo old, raising Tilipia, and lettuce, put in a few tblps table sea salt a while back, what is the correct salt to use, how much more should I add, have 80 gal tank, plus about 5 gal in troughs
You want to avoid table salt that has iodine or anti-caking agents in it. Iodine is bad for the bacteria and the anticaking agents can cloud water a bit and might not be that good for fish and bacteria either.

How to measure salt. Well in metric, much easier, 1 gram per liter is 1ppt. So if you can convert your 85 gallons into liters using one of the online conversion charts and then measure salt by weight (dissolve it in some system water before pouring it into the system as salt crystals can sit on the bottom and if a fish rests against them they can get burned.)

Tilapia can take quite a bit of salt but most plants don't want really high salt so for a general tonic and trace element supplement, somewhere between 1 and 3 ppt is probably appropriate.
To add to TC's information, if a fish is scaleless, it is likely to be sensitive to salt. I've always half-dosed salt and meds whenever I've had scaleless fish. For example: catfish are a scaleless fish, as are loaches, and a lot of corydoras.

I use basic aquarium salt to salt my tank per their instructions of use, and I also dissolve it completely before I add it to prevent salt burns. It's usually a tablespoon per 10 gallons of water for tropical fish, so I go for a tablespoon per 20 gallons. Metric sounds so much easier, TC.

A quick and easy online converter is the WolframAlpha Computational Knowledge Engine. You just type "85 gallons in liters" in the search bar and it will provide the info you seek (in this case, it's 321.8 liters).

Also, I hardly do more than a 25% water change ever, so I won't add salt back in until after I've changed at least 50% of the water and can ensure that it won't get over salted. I also don't have a salt tester, but should I change to edible fish, I might get one.

Whenever I have gotten outbreaks of diseases in my fish like ich, I always turn up the heat a few degrees and increase the salt the tank. This works like a fever in that it provides an increased immuno response within the fish, and the salt will take care of the cause. I also add in more of my bacteria culture to keep it protecting the fish. Turns out that the major retailer, Petco, uses this method whenever they have an outbreak and the corporate office refuses to let the stores use medications because they invariably cause secondary infections.
Aloha all- I've just added salt to my pond after seeing plenty flashing in my koi and comets, and other signs of parasites, with a targeted salinity of 3 ppt. I was just wondering what to expect for the compost worms in the GB. I've already seen a few come to the surface when the GB fills- will the salt kill them all? Should I grab the ones that surface and put them back in the worm bin until the three week treatment is over? Thanks -- Shawn
Hum, I'm not sure the exact situation with salt and the worms but I think 3 ppt is well within tolerance for the worms. If they seem really affected by the salt, then you might simply place a flower pot with moist compost on top of each grow bed and the worms can escape to that if they are really distressed. (I've found this is a fairly easy way to collect some worms from a grow bed too.)
Nice trick with the flower pot- I love simple stuff like that! Thanks for the reply TC. I had to excavate around my standpipe in order to improve it, and found lots of healthy and happy worms, so I think it will be ok. The initial cycle that may have bothered them may have been a bit stronger salinity, but I'm sure it balanced out quickly after a few cycles.

TCLynx said:
Hum, I'm not sure the exact situation with salt and the worms but I think 3 ppt is well within tolerance for the worms. If they seem really affected by the salt, then you might simply place a flower pot with moist compost on top of each grow bed and the worms can escape to that if they are really distressed. (I've found this is a fairly easy way to collect some worms from a grow bed too.)

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.

I  searched for information that might confirm the idea that salt does not necessarily have to be NaCl.  Here is a link to a product called of all things Cichlid Lake Salt where the benefits of other trace elements are promoted.

Guaranteed Analysis

Calcium (min)
3.24 %
Calcium (max)
3.50 %
Magnesium (min)
11.83 %
Potassium (min)
10.08 %
Sodium (min)
3.53 %
Sodium (max)
3.75 %
Aluminum (min)
0.90 mg
Iodine (min)
0.02 mg
Iron (min)
0.20 mg

I know I'm often a sucker for these kind of ads, and tend to throw time and money at things that don't matter, so I'm curious to hear what others think.   I'm guessing that some of these minerals would be available from the fish food so the need for Cichlid Salt may not be necessary. 

But it still leaves me wondering about my original premise that other salts/minerals can reduce the need for NaCl and thereby benefit both fish and plants.



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.

I never got a firm answer from anyone but at one time I had asked if potassium chloride might be a better salt to use for nitrite protection while at the same time providing potassium to the system.   See it is actually the chloride ion that can help bond with nitrite to protect the fish from nitrite poisoning to an extent but I wasn't sure if it had to be from Sodium Chloride or if it could come from something else like potassium chloride and leave the potassium available for the plants.

As I said, no one really answered me when I asked that years ago.  I have used some potassium chloride in my old systems back before I found a local source where I could get seaweed extract.

Now I also know people who swear by using SEA 90 salt which is a dehydrated sea water from a arid location so most of the trace elements in the sea water are not lost to leaching and there fore the SEA 90 salt is a good source of all the stuff good sea water has in about the same ratios as sea water.  I haven't used it myself so I can't really comment further.

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