IFC Aquarium Fertilizer Calculator

[TheGreatScape]

I’m genuinely surprised that the ratio of potassium to sulphur can be different in a chemically bonded chemical. Also, they don’t state the purity of the product. Given your percentages, I’m left wondering what else is in there…anti caking agent presumably. Perhaps some of the chemists on the forum can shed some light on this, @Andy Pierce ?

Yeah, I didn't know this was a thing, either. It was only after comparing the product from NilocG to one that I found locally that I noticed that the percentages vary. Unfortunately, in both cases, the manufacturer only provides this guaranteed analysis and does not include any information about the purity.

 

[TheGreatScape]

neither. You want K2SO4.

APC Pure | Product | Potassium Sulphate 97.5% - 99.9%

APC Pure is a leading chemical and reagent manufacturer

apcpure.com

I just noticed:

This one is actually 50% K and 17% S. Looks like majority of them are around this 50% K and 17-20% S range

 

[Zeus.]

I should be looking for whichever supplier can offer me the highest % of K

Well knowing the K% allows you to calculate the mg of K per gram of product, a higher K% doesn't always indicate its purity. A pure salt of K2SO4 has 44.87% K and 18.40% S and a pure salt of KCL has 52.45% K and 47.55% Cl
There will be other K compounds in the salt as well.

GLA and NilocG both offer this 52% K and 18% S mix.

which IMO suggests its mainly K2SO4 with some KCL along with other minor salts, I would say GLA and NilocG products are pretty good for the job.

 

[dw1305]

Hi all,

The values I pulled from are K2SO4 from NilocG and another supplier. I see Green Leaf Aquarium's K2SO4 also has a similar analysis:

K2SO4 Guaranteed Analysis:

• K2SO4 0-0-52
• Soluble Potash (K2O) - 52%
• Sulfur (S) - 18%

Will using these mess up the calculations since some suppliers have K2SO4 with a guaranteed analysis of 42.5% K and 17.0% S while others have 52% K and 18% S

This one is actually 50% K and 17% S.

That still isn't quite right, if it is 50% (K2O) x 0.83 = 41.5% K

It is just because horticultural fertilisers express the potassium (K) content as "potash" potassium oxide (K2O), this means to convert from K2O to K you need to multiply by 0.83. The details (and calculations) for potassium and phosphorus (P) (also expressed as an oxide) are in <"percentage for dry fertilizers">.

Potassium sulphate doesn't form any hydrates <"Targeting Potassium">, so it is always K2SO4, although there maybe other cations present if it was derived from a mineral deposit <"Seachem method of potassium dosing"> and not further refined.

cheers Darrel

 

[dw1305]

Hi all,

The health store that sells this lists it as 100% Potassium Chloride. Unlike with K2SO4, they don't list the % K and Cl.

Simple enough, you just need the RAM of potassium (K) and the RAM of chlorine (Cl) to give you the RMM of KCl.

<"Potassium - Wikipedia">= 39.1 + <"Chlorine - Wikipedia"> 35.5 = <"Potassium chloride - Wikipedia"> = 74.56 and

39.1 / 74.56 = 52.4 % K and 100 - 52.4 = 47.6% Cl

In a 100-liter aquarium, adding 10 mg/L of potassium via KCl weekly would introduce 16 mg/L of chloride each time. Over 10 weeks, chloride could accumulate to an additional 160 mg/L, potentially surpassing safe levels.

It is less than that (I don't know where the 16 mg / L came from? It should be ~ 9.1 mg / L and 19.1 x 0.476 = 9.1)). The "19.1" is the amount KCl to give 10 mg / L K, but I understand your concerns.

From my understanding, Chloride ions introduced into the aquarium do not break down or get consumed significantly by organisms; therefore, if one skips on water changes and dosing for weeks, eventually, the buildup will go to dangerous levels.

Yes and no, it really depends on a number of factors. I like to keep chloride (Cl-) (and sodium (Na+) ions levels low for the reason you give, but if you had hard water and kept hard water fish and plants? It wouldn't bother them at all. As an example <"Lake Tanganyika"> has about 130 mg / L Cl-.

cheers Darrel

 

[TheGreatScape]

Hi all,

Simple enough, you just need the RAM of potassium (K) and the RAM of chlorine (Cl) to give you the RMM of KCl.

<"Potassium - Wikipedia">= 39.1 + <"Chlorine - Wikipedia"> 35.5 = <"Potassium chloride - Wikipedia"> = 74.56 and

39.1 / 74.56 = 52.4 % K and 100 - 52.4 = 47.6% Cl

It is less than that (I don't know where the 16 mg / L came from? It should be ~ 9.1 mg / L and 19.1 x 0.476 = 9.1)). The "19.1" is the amount KCl to give 10 mg / L K, but I understand your concerns.

Yes and no, it really depends on a number of factors. I like to keep chloride (Cl-) (and sodium (Na+) ions levels low for the reason you give, but if you had hard water and kept hard water fish and plants? It wouldn't bother them at all. As an example <"Lake Tanganyika"> has about 130 mg / L Cl-.

cheers Darrel

Hi Darrel, thank you for the informative response. The easiest accessible Potassium Sulphate available near me list the composition as:
K : 425 g/kg (42.5%)
S : 170 g/kg (17.0%)

Based on the formula you have given me, this one would give 35.27mg/l (ppm). Quite low compared to Niloc & GLA. I will search locally at more farming supplies stores and see if any offer a more superior product. In the above product, the cost is $5/kg. I have also found a lab supplies store selling Potassium Sulphate Exra Pure K2SO4 AR 500g at around $10 (4X more expensive) and Potassium Nitrate for $96/500g compared to Niloc, which sells the same amount of KNO3 for $5. The lab grade K2SO4 I am awaiting the documents. Although pricey, it would still work out cheaper for me compared to buying overseas and shipping, so I don't mind the price if it's worth paying the extra compared to the 5$/kg option.

I'm definitely not going to get lab-grade KNO3, though. Just out of curiosity, why are there such huge variances in pricing for KNO3?

My tank is more on the soft-water side. I keep discus, neon, cardinal, rummynose, L333 Pleco's and Cory's which prefer soft water and lower pH ranges. The water is mostly around the 6pH or lower mark; with CO2, it goes even lower. The 16mg figure was incorrect. It should've been 9.06 mg/L as you pointed out. At this rate, even without a water change being done for 10 weeks, it still wouldn't be dangerous so I guess it's a good option. Pricewise it works out to around $5/500g.

 

[dw1305]

Hi all,

Just out of curiosity, why are there such huge variances in pricing for KNO3?

Lab. (technical or food) grade chemical are a lot more expensive than fertiliser grade, just because they are more refined. "Analytical grade reagents (AGR)" are an order of magnitude more expensive (and of higher purity) again.

Unless you are making up standard solutions (to use with analytical grade equipment)? You never need AGR. For 99% of other uses fertiliser grade is absolutely fine and even technical / food grade is purer than you ever need.

You can use the tech. grade, the lab. grade is for analytical work (like making up standards) and is ultrapure.

The level of impurities in the tech grade will still be vanishingly small. The way I think about is in terms of "lorry loads". So using that as an analogy, the lab. (analytical) grade has a grain of sugar in a lorry load of salt, and the tech. grade a sugar cube in a lorry load of salt.

As an example we are suspect that Seachem buy a <"polysulphate fertiliser">, and just re-packet, and re-brand, it as <"Seachem Equilibrium"> - <"Polysulphate - Origin Fertilisers">.

cheers Darrel

 

[dw1305]

Hi all,

The easiest accessible Potassium Sulphate available near me list the composition as:
K : 425 g/kg (42.5%)
S : 170 g/kg (17.0%)

Based on the formula you have given me, this one would give 35.27mg/l (ppm)

So that is K2OS4.

The RAM of potassium (K) = 39.1, sulphur (S) = 32.1 , oxygen (O) = 16. To get the RMM is (39.1 x 2) + 32.1 + (16 x 4) = 78.2 = 32.1 + 64 = 174.3 and 78.1 / 174.2 = 45% , so near enough.

When you 10g of K2SO4 you've added 4.5 grams of potassium and you need ~23g of K2SO4 to yield 10g of potassium. So not much different to the KCl, in percentage potassium, but a smaller amount of anion (SO4--) because we have 2 K+ ions for every single SO4-- (we can ignore the 4 x oxygen).

cheers Darrel

 

[TheGreatScape]

Hi all,

Lab. (technical or food) grade chemical are a lot more expensive than fertiliser grade, just because they are more refined. "Analytical grade reagents (AGR)" are an order of magnitude more expensive (and of higher purity) again.

Unless you are making up standard solutions (to use with analytical grade equipment)? You never need AGR. For 99% of other uses fertiliser grade is absolutely fine and even technical / food grade is purer than you ever need.

As an example we are suspect that Seachem buy a <"polysulphate fertiliser">, and just re-packet, and re-brand, it as <"Seachem Equilibrium"> - <"Polysulphate - Origin Fertilisers">.

cheers Darrel

Ah, I see. Thanks for the information. I think I'd rather go for the cheaper stuff then. It's easily accessible and good enough for this use case. Also, I agree with the findings regarding the Seachem one. I wouldn't put it past them to do simple repackaging, branding, and marketing. That source you listed, Aquarium Science, has researched and debunked quite a few of their product claims.

 

[TheGreatScape]

@Zeus. How would I override the IFC calculator values to set my K2SO4 according to the following so that I get the correct PPM and amounts to add to the container:

The RAM of potassium (K) = 39.1, sulphur (S) = 32.1 , oxygen (O) = 16. To get the RMM is (39.1 x 2) + 32.1 + (16 x 4) = 78.2 = 32.1 + 64 = 174.3 and 78.1 / 174.2 = 45% , so near enough.

When you add 10g of K2SO4 you've added 4.5 grams of potassium and you need ~23g of K2SO4 to yield 10g of potassium.