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Sodium and plants

GlassWalker

GlassWalker

Member
Joined
30 Jun 2014
Messages
205
Location
Swindon
I have a feeling this might be a "how long is a piece of string" type question, but how much sodium do you need before there are adverse effects on plants? I presume different plants would have different tolerances e.g. marine plants might like a lot of it! But here I'm of course more interested in typical tropical freshwater aquarium plants.

In case you're wondering why I'm asking this, my main tank is a heavily stocked with fish and that chews through KH like it is going out of fashion. On top of water changes, I intend to start dosing to help keep it from getting too low.

I did a rough calculation earlier. Since I have dosing bottles that makes it easy for me to apply. They're 500ml, and by my calculations I can use 91g of potassium bicarbonate per 500ml to give a solution, which at 20ml in 100L would give 1 dKH and 14mg/l potassium. My water is already high in potassium to start with, and I'm dosing EI on top of that... so I'm half debating if I should use sodium bicarbonate. That also has a minor plus in that I already have a mix of that prepared for my marine tanks. I guess I'm more worried about the presence of sodium than I am about a possible excess of potassium. If I used sodium bicarbonate, I'd be adding 8.3mg/l of sodium per dKH.
 
There are no negative effects of high potassium.
I routinely dose Potassium at values exceeding 100ppm K+ so it's a pointless waste of time worrying about K+ toxicity.
Here is a tank dosed at approximately 130ppm K+
If people want to worry then they always choose to worry about CO2 above everything else.
8394080097_da3efbd025_c.jpg


On the other hand, it should not be too much of a problem using Sodium Bicarbonate to adjust alkalinity, but it depends on the plants. The range is vast. Florida lakes, for example have Na++ concentrations from about 10ppm inland to over 1000ppm in areas near the coast, so there is some adaptability. Other plants originating from areas where there is no coast or saline source may not be as adaptable. Generally it's best to avoid using water from a water softener which uses salt as these will have very high Sodium concentrations.

Cheers,
 
GlassWalker said:
In case you're wondering why I'm asking this, my main tank is a heavily stocked with fish and that chews through KH like it is going out of fashion.
Click to expand...

Hi All

Can someone please explain what the OP means by this statement? I'm knew to water chemistry and planted tanks and do have a really soft water due to using RO water. Can this cause problems if the dKH is too low?

Best wishes

Bhu
 
Thanks for the reassurances on potassium. I'll stick to the plan of using potassium bicarbonate then as it is likely less risky than using sodium.

On the KH consumption, for now, pretend there are no plants in tank. We only have fish and a biofilter provided by an internal or external filter populated with bacteria (or whatever it is the latest research says they are). When those bacteria oxidise ammonia through to nitrate, they also consume KH in the process. If there aren't many fish, then normal water changes alone are generally ok to restore that and you don't have to worry about it. In the case of one of my tanks, I'm running soft water (remineralised RO) and a LOT of fish, pushing the upper limits of what's considered a good amount. They're also very hungry fish and take a lot of feeding. I haven't taken close measurements but I do note my KH value drops <1.0 by the time a water change comes around. I'm thinking I want a bit more buffer than that which can be provided by extra dosing and/or altering the balance of the remineralisation salts.

I don't know if plants affect the above process significantly. They will likely consume some of the ammonia before the filters get to it, but I don't know if they similarly consume KH in any significant amount. At least, I don't recall ever hearing of using (bi)carbonates as a fertiliser.
 
Hi all,
GlassWalker said:
I'm running soft water (remineralised RO) and a LOT of fish, pushing the upper limits of what's considered a good amount. They're also very hungry fish and take a lot of feeding. I haven't taken close measurements but I do note my KH value drops <1.0 by the time a water change comes around. I'm thinking I want a bit more buffer than that which can be provided by extra dosing and/or altering the balance of the remineralisation salts.
Click to expand...
You could just add some of your potassium as KHCO3 if you are worried about the dKH falling. Once they are in solution every K+ ions is the same, it doesn't matter what compound they came from.
ian_m said:
"Sodium is undesirable in a freshwater aquarium..."
Click to expand...
Pretty much, there is actually similar reserves of sodium and potassium on the earth, but because plants don't have a sodium requirement the sea is salt with NaCl (the Cl has accumulated for similar reasons).

cheers Darrel
 
My original concern other than sodium was possible buildup of potassium. As already noted, this doesn't sound like an problem at any level I'm likely to come across. I did wonder if there was a way to reduce the proportion of potassium in EI, but if there is I can't think of an easy way. In other words, what else would I swap it with? I'll leave it there.
 
Hi all,
GlassWalker said:
I did wonder if there was a way to reduce the proportion of potassium in EI, but if there is I can't think of an easy way. In other words, what else would I swap it with? I'll leave it there.
Click to expand...
If you want to add more dKH just add some KHCO3, it will raise conductivity and dKH, but other than that it won't have any adverse effects.

It is the same with anion exchange resins, you can always substitute KCl for NaCl when you re-charge them, the cation doesn't matter.

A lot of commercial re-mineralising salt mixes have NaCl or NaHCO3 in them as a "filler", because it is the cheapest option, and all the talk about "osmotic pressure" etc. is just "smoke and mirrors".

Swapping compounds in EI is probably more a nitrogen problem than a potassium one.

Potassium nitrate (KNO3) supplies both your K and N. Any other potassium compound could be used for the K, and a compound like KCl would be widely available.

Suitable nitrates would be Mg(NO3)2.6H2O or Ca(NO3)2.4H2O, but they don't offer any advantage of KNO3. Details are in the <"How much calcium nitrate ...."> & <"Spezial N - Nitrogen fertilizer"> threads.

cheers Darrel
 
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ceg4048 said:
On the other hand, it should not be too much of a problem using Sodium Bicarbonate to adjust alkalinity, but it depends on the plants. The range is vast. Florida lakes, for example have Na++ concentrations from about 10ppm inland to over 1000ppm in areas near the coast, so there is some adaptability. Other plants originating from areas where there is no coast or saline source may not be as adaptable.
Click to expand...
Would you care to expand on this? Has anyone compiled a list of plants showing their relative (in)tolerance to Na++ and the actual corresponding Na++ numeric concentrations in ppm? How well (or not) would Echinodorus varieties, for example, cope with sodium ions? I ask because I'm concerned that the remineralizing RO salts that I use can raise the Na++ concentration to 30ppm. I have no way of knowing before planting if that's good or bad.

Thanks in advance.
 
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I think I would be more concerned about the effects of sodium on fish especially Amazonian species than I would about Potassium for plants. In the EI article on UKAPS the recommendation for potassium is 30ppm per week. I knocked up a little chart just for my own use so whatever size tank I'm dosing I can quickly work out how many mils out of the same bottle should go into each tank obviously depending on the tank volume so I just have one EI macro mix bottle sitting about I can use on every tank.

EI Dosing Final.png

As you can see from that, even at what is considered to be EI values of PO4 and KNO3, weekly you would be adding about 20ppm of potassium so you still have another 10ppm you could add via the potassium bicarbonate. Plants tend to get through a bit of potassium anyway. In my low tech tanks where I either don't dose kno3 or po4 because the lighting is so low and fish waste provides enough I tend to find that it's always the pot that is needed first. Soon as I add some potassium sulphate the plants perk up. Like Clive says though you could even be up from the 30ppm EI standard without worry, 5x that in Clives case :eek:

Aquarium Plant Foods do Magnesium Nitrate which you could swap out for potassium nitrate in your EI mix and just carry on with the potassium carbonate which should lower the potassium levels a touch if it concerns you. Could you not just also bag up some chick grit in some tights or the various filter mesh bags you can buy and pop it in your filter canister? That should buffer up your KH without adding further sodium or potassium.
 
jaypeecee said:
Would you care to expand on this? Has anyone compiled a list of plants showing their relative (in)tolerance to Na++ and the actual corresponding Na++ numeric concentrations in ppm? How well (or not) would Echinodorus varieties, for example, cope with sodium ions? I ask because I'm concerned that the remineralizing RO salts that I use can raise the Na++ concentration to 30ppm. I have no way of knowing before planting if that's good or bad.

Thanks in advance.
Click to expand...
No, sorry, I have not seen a list. Folks just accept that Sodium is not nice and simply avoid using it. Are you certain that your agent of choice uses Sodium? It would be very unusual. You haven't mentioned the brand but there are many products on the market that don't use Sodium.

In any case, I don't think 30ppm or the buildup due to water changes will be too much of a problem based on some studies done (at least for those particular species), such as https://www.google.com/url?sa=t&rct...08223382.pdf&usg=AOvVaw1gM_fpSvV0HkxJW7scwpyH
as well as https://www.jstor.org/stable/1351922?seq=1#page_scan_tab_contents
where the numbers reached into the thousands of ppm. Those species are fairly hardy though so it really isn't clear how to apply these values to the more sensitive species such as carpet plants and so forth.

Cheers,
 
ceg4048 said:
No, sorry, I have not seen a list. Folks just accept that Sodium is not nice and simply avoid using it. Are you certain that your agent of choice uses Sodium? It would be very unusual. You haven't mentioned the brand but there are many products on the market that don't use Sodium.

In any case, I don't think 30ppm or the buildup due to water changes will be too much of a problem based on some studies done (at least for those particular species), such as https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwjXsf_pptzcAhVKr1QKHbDVBlMQFjAAegQIABAC&url=https://pdfs.semanticscholar.org/0267/c4beb3a9bf85910fe996a42e4ebf08223382.pdf&usg=AOvVaw1gM_fpSvV0HkxJW7scwpyH
as well as https://www.jstor.org/stable/1351922?seq=1#page_scan_tab_contents
where the numbers reached into the thousands of ppm. Those species are fairly hardy though so it really isn't clear how to apply these values to the more sensitive species such as carpet plants and so forth.

Cheers,
Click to expand...
Thanks for your reply.

The product to which I am referring is Re-Mineral Tropic, which is made by Tropic Marin. I have an email from them confirming that, when mixed with RO water as instructed, the resulting sodium concentration is 31.9mg/l. They are of the view that this is not a problem but I see no reason for the sodium to be in their product in the first place. Consequently, I will soon switch. I am tempted to go for the mix suggested at http://www.theplantedtank.co.uk/RO.htm. Or one of Seachem's offerings.

Thanks also for the links, which I will read this evening.
 
Hi all,
jaypeecee said:
They are of the view that this is not a problem but I see no reason for the sodium to be in their product in the first place
Click to expand...
dw1305 said:
A lot of commercial re-mineralising salt mixes have NaCl or NaHCO3 in them as a "filler", because it is the cheapest option, and all the talk about "osmotic pressure" etc. is just "smoke and mirrors".
Click to expand...
It is in the salt mix as a cheap filler.
dw1305 said:
Pretty much, there is actually similar reserves of sodium and potassium on the earth, but because plants don't have a sodium requirement the sea is salt with NaCl (the Cl has accumulated for similar reasons).
Click to expand...
I've subsequently found out that this isn't strictly true, and that most of the Na+ Cl- ions in sea water are there from strictly geological processes (hydrothermal vents) and the the biogenic effect is comparatively minor.

cheers Darrel
 
I'm sure I've seen it specifically stated that Re-min Tropic doesn't contain NaCl. I know it's popular with discus keepers. My plants seem to grow fine with it, but in fairness they are the more easy/hardy types.
 
The Na may be showing up as Na Phosphate, Na Nitrate etc ... the sodium version of various salts is always cheaper than the K (potassium) version
 
Like DW says then, using sodium as a cheaper filler than potassium.

Sent from my STH100-2 using Tapatalk
 
tam said:
I'm sure I've seen it specifically stated that Re-min Tropic doesn't contain NaCl.
Click to expand...
Yes, that would stack up. I was informed by Tropic Marin that "In Re-Mineral Tropic sodium and chloride are not in the form of common table salt".
 
Wouldnt it be easier to chuck some CaCO3 in the filter. Ie some coral rubble ..that will self regulate your Kh .
 
Hi Folks,

I'm re-visiting this thread to add a recent observation. Although I don't use tap water in my tanks, I note that sodium in my tap water last year ranged from 19.0 - 37.6 mg/l. Not only that but the PCV (Prescribed Concentration or Value) is currently 200 mg/l. These figures are taken directly from the South East Water Crowthorne Water Supply Zone annual report 2018.

Food for thought?

JPC
 
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