Optimising Your Aquaponics System

[Crusty]

One to one, KCl Same as NaCl.

I guess it comes down to whether chloride ions are just a big a problem as the sodium ions. If so then substituting with KCl probably isn't going to achieve much.

Mmmm Sodium chloride is apparently 40:60 sodium:chloride.

Here is a little doc from a google search...
http://www.jbc.org/content/1/4/363.full.pdf
It is only one view but searching about keeps netting the similar or the same results.

It may be remarked that for these plants potassium chloride, magnesium chloride, and magnesium sulphate are nearly as toxic as sodium chloride, while calcium chloride is not far behind in this respect. We have here a striking illustration of the remarkable fact that when salts, individually poisonous, are mixed together in the right proportions their toxicity totally disappears. Such a mixture has been termed a balanced solution by Loeb,

More to the point, there really is no need to manage the toxicity of nitrite with chloride in a well managed (set up) system as you do not have nitrite spikes. The additional protection the fish receive from the addition of salt is negligible in comparison to the loss of growth in the plants and the accumulation of a very potentially toxic element. Considering that most water if it is not distilled will contain adequate levels of chloride for the plants (possibly the fish?), I see no benefit in adding any at all in small back yard systems. Manage the water quality and the chances of using salt are very low.

[arachdog]

Mmmm Sodium chloride is apparently 40:60 sodium:chloride.

Yeah I realized after I went to bed you were probably talking on a weight for weight basis not atom for atom.
K=39
Na=23
Cl=35 (btw looks like I got the weight wrong for that other calc I did. I won't bother redoing it since I'm sure the general care factor is approaching zero)

39/(39+35)
=53% Potassium
Which I guess is bad since it means you'd need to add more to get the same effect on nitrite toxicity.

Here is a little doc from a google search...
http://www.jbc.org/content/1/4/363.full.pdf
It is only one view but searching about keeps netting the similar or the same results.

Yeah I wasn't think so much about it's toxicity. More about the time it would take to clear the system.

More to the point, there really is no need to manage the toxicity of nitrite with chloride in a well managed (set up) system as you do not have nitrite spikes. The additional protection the fish receive from the addition of salt is negligible in comparison to the loss of growth in the plants and the accumulation of a very potentially toxic element. Considering that most water if it is not distilled will contain adequate levels of chloride for the plants (possibly the fish?), I see no benefit in adding any at all in small back yard systems. Manage the water quality and the chances of using salt are very low.

Yeah I agree. It's very much a band-aid solution. But once you've stuffed up I guess it has the advantage of being quick to apply. Unlike the proper fix (more bio-filtration) which could take weeks to kick into action.

[Crusty]

=53% Potassium
Which I guess is bad since it means you'd need to add more to get the same effect on nitrite toxicity.

Interesting though and very marginal. Considering the potassium will be taken up by the plants and from memory, common deficiencies are potassium, calcium and iron it would be more benefit compared with using sodium chloride. From a band-aid solution point of view, the use of potassium chloride may prove to be more beneficial in an aquaponic system than sodium chloride.
The difference is so small I doubt it is important. If someone could check my math, as I am prone to incorrect calcs on the fly.... Oh forgot to mention that the very small amounts used for nitrite toxicity, I doubt that amount of salt would cause any issues for the plants at all. My main concern is those running 1 to 2g/L sodium chloride as a general rule....

I want to add another little nugget to this conversation for consideration. If you were to contact your local water supply (town water) and ask them what the chloride content of the water in your tap is, you may be able to use this instead of any salt, by a simply dilution exchange....

Yeah I wasn't think so much about it's toxicity. More about the time it would take to clear the system.

I have no idea how long it would take for chloride to be used up as it comes in so many shapes I would expect it to be constantly present.

Yeah I agree. It's very much a band-aid solution. But once you've stuffed up I guess it has the advantage of being quick to apply. Unlike the proper fix (more bio-filtration) which could take weeks to kick into action.

Yeah, it can be handy to have about ready to go. I am liking this alternative though. There is definitely some potential there.

[arachdog]

I want to add another little nugget to this conversation for consideration. If you were to contact your local water supply (town water) and ask them what the chloride content of the water in your tap is, you may be able to use this instead of any salt, by a simply dilution exchange....

Good point. I would think nearly all town water supplies would be over that. In actually fact most water supplies in general unless your using rainwater or glacial melt water.

You've not really touched on what your opinion is of the other reasons people reportedly use salt (in the higher 1-2ppt range). ie. parasite inhibition and enhanced slime coat. Do you think there's a real benefit to be had here ?

I actually took the time to read the link you posted and it would seem to me the main take home message would be if your going to salt your system for whatever reason, you'd be far better of using a balanced sea-salt mixture than pure sodium chloride. I'd like see more research and if possible an explanation for this effect before I got right behind it though.

[Crusty]

You've not really touched on what your opinion is of the other reasons people reportedly use salt (in the higher 1-2ppt range). ie. parasite inhibition and enhanced slime coat. Do you think there's a real benefit to be had here ?

As I have said before, I am not certain the benefits to the fish outweigh the negative impact on the plants, especially in such small scale, low density environments. At a commercial level, sure it can be inexpensive and beneficial.

If you are not handling your fish, it would be rare for them to suffer from osmotic stress (plants suffer this with the addition of salt), one of the reasons for low treatments (0.5 - 1g/L) when transporting fish. I watched a video recently that showed a fish being ripped out of a tank using a fishing landing net, bashed about the side of the tank, held out of water, hands rubbed over it, in a display of really poor knowledge of fish handling. In this case, a salt treatment of 1 to 2g/L will prevent osmotic stress and reduce the risk for bacterial infections from injury. Though I doubt a fish being handled in such a way would survive for more than a day or two. But I get sidetracked...

Is there any evidence outside of aquarium circles that shows treatments lower than 5g/L prevent parasite infections? I would be interested to see this. Sure after a parasite infection a prolonged submergence is recommended at rates >5g/L after the initial 10 to 30g/L treatment. Another interesting nugget is salt treatments claim to prevent or even heal fungal infections, but again we are talking about a very questionable aquarium trade. It seems to me the aquarium voodoo has leaked into aquaponics.

The main point here is prevention through water quality management and proper care for the fish. Do this and you will not need salt in your back yard aside from an initial treatment when you receive your new fish. That is done before the new fish are introduced to your production unit.