Backyard Aquaponics
A place to discuss aquaponics

I am waiting for a Blue Lab Guardian Monitor, along with its accessories, to be delivered to me. It should arrive, hopefully, by this weekend.



Anyway, one of the options it has, is to test for Electrical Conductivity. So, I was wondering if salinity was the same as electrical conductivity.

I would go into the reason(s) why I didn't ask the sales guy about this, but I won't. I will just leave it at, he seemed to be more of the read_from_the_monitor sort of guy, rather than someone who actually knew his product.

Thanks for any input here.

EC is a surrogate for salt levels.... and it literally reflects 'salts' in their various forms.

(recall Acid + base = water + salts)

you cannot assume that EC reflects NaCl unless you have just added NaCl.
[so you can use it to check salt levels after adding salt]

in hydroponics and aquaponics you will see big swings in EC when you add mineral fertilisers and also if you have a lot of nitrates.

Im still unsure to this day whether EC has value in backyard AP. Minerals can give unreliable readings therefore rendering the numbers unsure. Although I don't have much experience in this area sorry.

This stuff keeps me confused.

On the 15th, I added 1.4 kgs, or 1 ppt of salt.

Tested today, after a 120 liters water change, and cleaning the RFF.

pH 7.4
Ammonia .25 ppm
Nitrites 2.0 ppm
Nitrates 5.0 ppm

Siphoned 60 liters from RFF. Added 60 liters back.
Added an additional 60 liters to the sump.

Adding salt really shouldn't have much effect on your readings unless you exceed the amount that your bacteria can tolerate (which I'm pretty sure you haven't unless you have been adding way more than 1 ppt). I don't know where you're at with your system since I haven't looked for your other thread but you might have too many fish for the filtration or the filter is not working as well as it needs to for some reason.

Only 10 fish in a tote. None fully grown yet.

Total system capacity is under 1,500 liters.

Maybe my moving media bio-filter isn't established yet?

From New Zealand to Cambodia - 48 hours. Pretty good.

To answer the original question, on your meter, the EC, ppm, and TDS are all indicating the same thing. There is a simple conversion from one to another by multiplying by a constant. The constant is probably listed in the manual or online documentation.

I use a similar measure to make sure nothing is grossly wrong with the water. For example, a sudden change would mean something was added and a buildup over time might indicate something is in top up water but not being absorbed by plants. Also it's a good confirmation to check salt levels after adding NaCl to treat ich. In my system, I salted to 1ppt and I've been watching as tds slowly falls with time. If I need to salt again, I know how much is left over from the last time I added.

Hi Scott, thanks for replying. I have been trying to locate fittings to pipe my drain from my beds. So, I haven't been on as much as I would like.

As always, I appreciate your input and advice.