Optimising Your Aquaponics System

[GaryD]

Hi,

For those who may be interested...........Optimising Your Aquaponics System - Part 1 (http://www.microponics.net.au/?p=960).

Gary

[GaryD]

Hi,

Paul (aka Crusty) posted a comment on my blog in response to Optimising an Aquaponics System - Part 1 and I thought that it was too valuable not to be should be shared with APHQ members.


Well said.

I would go easy on the salt addition, especially if you do not know how much salt is in the system before you treat it (EC/TDS meter anyone?). Sure it provides benefit to the fish but in a well stocked and managed system, you will not really need it as a prolonged exposure. If you do it is best to treat the fish outside the system at a higher dose.

Remember sodium chloride is not taken up by plants to any degree, especially sodium (chloride in small amounts) and therefore accumulate. It is diluted when you top up your system with new water but generally, you will be exchanging, on average 5% of your water per week, which means it can take up to 20 weeks (5 months or longer in winter) to completely dilute the salt.

Sometimes in the back yard, having more tanks for treatment is not often the case, though it is a good idea. Also handing fish is not much fun for both the human and the fish, so permit me to provide you with a solution:


Lower the water level in your fish tank to half
Store that water elsewhere for reuse.
Increase the aeration with adequate air stones.
Treat the fish at the required salt level for the issue you are having (usually no more than an hour).
Then fill the fish tank back up again to dilute the salt by 50%. Fish treated, salt use reduced, fish not handled, no spikes in your hands, everyone happy.

Important to note, Aquarium stones are not adequate and if you do not have an air pump, I strongly suggest you invest in one sized for your set up. As the salinity of the water increases, the oxygen saturation of the water lowers so air is really needed.

I might add that any changes or disturbances, cleaning etc.. are best done when the temps are low, like now in Australia. It is good practice to make any big changes to your system when everything is happening a great deal slower (when it is cold). This will get everything sorted, clean and ready for the next growing season.

Keep in mind that for every 5C temperature increase, everything (nitrification, respiration, pooing, metabolism, feeding) increases by around 50%. So while all the organisms in your eco-system are having a rest, it is a great time to get everything nice and ready for the next growth season.

Trying to clean your grow bed in summer may have a negative effect on everything else living in the water with it.

Enjoy!

Thanks Paul........for some very useful tips. Your comments add real value to the blog post.

Gary

[arachdog]

Remember sodium chloride is not taken up by plants to any degree, especially sodium (chloride in small amounts) and therefore accumulate. It is diluted when you top up your system with new water but generally, you will be exchanging, on average 5% of your water per week, which means it can take up to 20 weeks (5 months or longer in winter) to completely dilute the salt.

It'll take a lot longer than that, in fact it will never be 'completely' diluted. You have to remember that each successive water change removes less and less salt. If you start with 2ppt then with a 5% weekly water change, after 20 weeks you still have .75ppt of salt in the system. Even after 40 weeks you still have .27ppt.

[Crusty]

It'll take a lot longer than that, in fact it will never be 'completely' diluted. You have to remember that each successive water change removes less and less salt. If you start with 2ppt then with a 5% weekly water change, after 20 weeks you still have .75ppt of salt in the system. Even after 40 weeks you still have .27ppt.

Good point.

If we are talking about replacing water that has evaporated and transpired not taking any of the water out (with salt in it), the salt will never be diluted at all, ever. In fact it will get stronger. As the water is evaporates/transpires, the salt is left behind, so it gets stronger, then diluting the stronger brings it back to the where it was... On the other hand, if you are removing water by back washing a filter, then arachdogs assessment stands. Some people will be doing both. Even most source waters will contain salt. For example if you are using town water to top up in Australian coastal towns, that water can contain on average 40mg/L salt and inland town water can contain up to 250mg/L. An EC/TDS meter will give you a higher reading due to the nutrient salts that also build up and this will also depend on the solids in your system. As you can see the variables go on and on. My example is just to give you an idea without rambling on about the many variables that effect the salt levels in any system, and caution the use of additional salt ("If you do it is best to treat the fish outside the system at a higher dose").

So Arachdog point, emphases the dangers of additional salt.
.

[GaryD]

Hi,

Of course, the whole dilution question is less of an issue if you are using the water to irrigate soil-based gardens or other growing systems that are not connected to your system.

Gary

[arachdog]

...in fact it will never be 'completely' diluted
Actually not entirely true thinking about it, there would be a finite number of water changes to achieve complete eradication. You wouldn't be able to calculate it exactly, but you could work out the probability that it would be achieved after a certain amount of water changes.

I got bored and had a go:

Nice simple example, 1 ton tank, 2ppt salt.
Weight of dissolves NaCl = 2000g
Tank size = 1000L
No of atoms in a mole =6.023E+23 (Avagadros constant)
Weight of 1 mole of Na=6.941g
Weight of 1 mole of Cl =70.906g
Total weight of 1 mole of NaCL = 77.847g

Total No of moles in tank = 25.69142035
Total number of molecules = 1.54739E+25

Then I whacked that number into a spread sheet and removed 5% of the atoms each time, surprisingly after 1130 iterations there would be less than one atom left. Of course that's not exact because when there's only a few atoms zinging around some of your water changes might not achieve anything at all. But it would be pretty close to that figure, a lot less than I thought to be honest.

Now if that kind of information isn't useful to the average backyard aquaponicist then I don't know what is. LOL. :)

[GaryD]

Now if that kind of information isn't useful to the average backyard aquaponicist then I don't know what is. LOL.
Yeah.......we should be selling this stuff.:rolleyes:

Gary

[arachdog]

On a slightly less esoteric note, has anyone considered using potassium chloride (KCl) instead of regular salt in this application? As I understand it its the chloride ions that have the detoxifying effect on nitrite so I see no reason KCl wouldn't work just as well, and the potassium would be absorbed by the plants far more quickly since its a macro-nutrient. But to be honest I haven't thought it through for very long, there might be a good reason not to do it.

[Crusty]

I think we may be getting off track here....


Actually not entirely true thinking about it, there would be a finite number of water changes to achieve complete eradication.

Then I whacked that number into a spread sheet and removed 5% of the atoms each time, surprisingly after 1130 iterations there would be less than one atom left.

Now if that kind of information isn't useful to the average backyard aquaponicist then I don't know what is. LOL. :)

lol even I had trouble with that one mate. If you were using demineralized water it would work...


On a slightly less esoteric note, has anyone considered using potassium chloride (KCl) instead of regular salt in this application? As I understand it its the chloride ions that have the detoxifying effect on nitrite so I see no reason KCl wouldn't work just as well, and the potassium would be absorbed by the plants far more quickly since its a macro-nutrient. But to be honest I haven't thought it through for very long, there might be a good reason not to do it.

It is used as a replacement salt (non sodium). I think it definitely has merit Arachy. Not giving it much thought either, but I would be interested to know the potassium:chlorine (chloride) ratio. That would give us the treatment level for nitrite. Anyone have this info? The other thing to watch for is too much chloride, the plants will not like it at all as chloride competes with nitrate uptake from memory... The potassium will be handy within that 7 to 14 days of flowering plants for sure.

Worth more thought.

[arachdog]

but I would be interested to know the potassium:chlorine (chloride) ratio.Anyone have this info?

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.

[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.