How can I accurately test salinity?

[Pygar]

I started to raise the salinity following early signs of Ich in goldfish, aiming for 0.3%. After adding 48oz of API salt to the 1800 litre pond I thought it best to test rather than overdose the pond so I bought a conductivity test meter and Ph Meter.

The issues I have are
a. I'm not entirely sure how to convert the UD reading to percentage (sounds simple but the info on the web is confusing)
b. My Pond UD is approx. 4600 which I believe should be around 0.3% but my tap water is over 7000! and is not salty. The pond was originally filled with this tap water treated with a water safe treatment. The water in the area is hard and therefore will have dissolved solids, probably carbon, magnesium and potassium ions. Does this mean that my meter is useless for testing the salinity? Is there any other way I can accurately test salinity.

Water temp daily range is 19C to 24C and Ph 7.8 to 8.4.

Good news is that the goldfish that had white patches appearing on it's sides has shown really good recovery, to the detriment of my browning Marsh Marigold. Sadly I think I accidentally suffocated the other Goldie that appeared to have Ich whilst quarantining. Other fish and frogs all look happy.

 

[Dave 54]

You can buy a salinity meter from any marine fish stockist however using salt as the initial treatment can cause problems........ if you need to treat with chemicals especially with a Malachite treatment as it becomes toxic in some cases especially if you have a high Ph, and as salt stays in the water and has to be removed by water changes before you can use it .
A tip about the salt you dont need to buy salt from a fish shop they say its medicated but this is a bit of a con , go to the supermarket and buy cooking salt its dirt cheap 75p for 3 kg.
If you must treat your fish with salt a better way to do this is a short salt water bath which is normally enough to get rid of parasites.
In the Marine side of our hobby they do the opposite an give them a short fresh water bath because its enough to kill the marine parasites .
Fresh water fish do not live in salt water and vica versa with marine fish, thats why they are fresh water fish .

Dave

 

[Pygar]

Thanks for the reply Dave, are the salinity meters anything different to a conductivity meter? My problem with determining the actual salinity using that method is that my tap water with close to zero salinity has higher conductivity than my pond.
Treating the individual is a great idea but I also I want to treat the whole pond to kill the resident Ich parasites, will then gradually change the water to drop to around 0.1%, only a small pond so no sweat. I'm a little concerned about using cooking salt as it all seems to have some cyanide compound as an anti caking agent.

 

[Dave 54]

Thanks for the reply Dave, are the salinity meters anything different to a conductivity meter? My problem with determining the actual salinity using that method is that my tap water with close to zero salinity has higher conductivity than my pond.
Treating the individual is a great idea but I also I want to treat the whole pond to kill the resident Ich parasites, will then gradually change the water to drop to around 0.1%, only a small pond so no sweat. I'm a little concerned about using cooking salt as it all seems to have some cyanide compound as an anti caking agent.

Weve been using it for many years now Pygar with no ill evects to our koi whatsoever table salt is the one you cant use if you want to rid the pond of ich your est bet would be to add Malachite or a good off the shelf treatment for it, you need to kill off the free swimming stages of this protezoan Parasite

Dave

 

[fishin4cars]

I prefer a refractometer. I use to use salinity meter for salt tanks, then used actual hydrometer. I also bought a Lp medic salt reader and out of the four refractometer worked best for me, and it has been rugged and accurate for several years with many more years of use expected.

 

[crsublette]

Are the salinity meters anything different to a conductivity meter?

Sorry, I overlooked this thread. Here is my 2 cents.

Shortish long Answer....

Since our context of salinity testing is for the sodium ion, then, personally, no, the conductivity meter will not reliably test for sodium salts, that is without the correct coefficient. Even then, still, a conductivity meter will not be as accurate as a salinity meter.

Digital salinity meters are essentially a conductivity meter with one huge difference, that is the proper coefficient is programmed into the device. TDS meters can be used to test for the water's gravity, that is sodium salinity; however, on some of these TDS devices, you have to choose your salinity coefficient.

Technically, in our context, TDS is written as Total Dissolve Solids; however, due to the methodology used in testing, this Total Dissolves Solids is incorrect. To be more correct, TDS should be viewed as Total Dissolved Salts.

If you still want to know how to use your conductivity meter to test for sodium salinity, then read this article, which I found from a quick Google, that is this... Measuring salinity, TDS and conductivity.

Also, generally, when talking salts, I also reference the thread, How much salt is safe/too much??.

You can use hydrometers, refractometers, or digital salinity meters, which are shown in this hyperlink.

Although, I agree with Larkin (fishin4cars). For your money and for as little time as you will use it, the refractometer would be best. I have used the digital salinity meter now for a while and it has become a pain to maintain since I do not use it that much at all.


Geeky Answer...

The conductivity meter (EC) is actually testing the electricity amongst the salt ions within solution, which indicates activity or potency. Total dissolved salts (TDS) meter tells you the volume of salts in weight within the totality of solution, except it is still a conductivity although with a different coefficient. TDS digital meter is most often the meter used for our type of salinity testing since it can be more reliably retrofitted, through some extra calculations, to test for sodium salts, which is sodium salts or water's gravity is what you want to test.

For our context of freshwater pond hobbyists, you want to test for sodium in weight within the totality of solution, that is mg/L or ppm or ppt.

I am guessing you are coming from hydroponic gardening? Not many refer to a salinity meter as a conductivity meter. Most often a "conductivity meter" (i.e., electronic conductivity, EC) is referred by folks whom are monitoring the potency levels in their solutions or if there is a presence of too much fertilizer in water or if the planting grow bed is failing, that is often measured in units of dS/m or sometimes in µ S/cm or mS/cm.

TDS is measured in units of mg/L or ppm, which is closer to what you want since you will then have to convert the ppm to ppt so then to determine the percent concentration of salts in weight within the solution.

 

[crsublette]

1) My problem with determining the actual salinity using that method is that my tap water with close to zero salinity has higher conductivity than my pond.
2) Treating the individual is a great idea but I also I want to treat the whole pond to kill the resident Ich parasites, will then gradually change the water to drop to around 0.1%, only a small pond so no sweat.

1) My problem with determining the actual salinity using that method is that my tap water with close to zero salinity has higher conductivity than my pond.

Due to using a conductivity meter, your account of what happened does not surprise me, that you found your "tap water with close to zero salinity has higher conductivity than pond", which is due to what the meter is actually testing. Your water may likely have a high concentration of various chlorides and other ions which is why your tap water his a higher conductivity than your pond even though it has zero salinity.

This is why I would not use a conductivity (i.e., EC meter) to test for salinity since it is using the wrong coefficient.


2) Treating the individual is a great idea but I also I want to treat the whole pond to kill the resident Ich parasites, will then gradually change the water to drop to around 0.1%, only a small pond so no sweat.

Most pond/aquarium medicines have carcinogenic compounds, that is stuff that can cause cancer when the water or plants/fish irrigated with that water is consumed by humans. So, in hobbies where the fish or vegetables/herbs grown from the pond water are to be consumed by humans, then salt is most often used to kill parasites and Ich is the most common form of parasite that is easily killed by salt. However, be careful with plants during the salinity duration since many plants cannot tolerate a high salinity.

So, whether it is malachite or some other pond/aquarium medicine or salt, it is all good just as long as you follow proper instructions and depending on your context.