K2SO4 (potassium) question - The Planted Tank Forum
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post #1 of 11 (permalink) Old 11-17-2016, 08:28 AM Thread Starter
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K2SO4 (potassium) question

Hello, I have an established 10 gallon low-tech tank that has been up for approximately six months, which I have just begun dosing with ferts and Excel.

I have a bottle of Seachem liquid potassium. If I do the math, the verbiage on the Seachem bottle tells me that 1.67 mL of this product will raise the K2SO4 level in 10 gallons of water by 3.33 ppm. My research reveals that the suggested ppm level of K2SO4 for a CO2 enriched aquarium should be between 10-20ppm, (10ppm for a tank without CO2, which I mention just for reference). The verbiage on the Seachem bottle recommends dosing K2SO4 two to three times a week.

The questions I have are: (the short of it is how do you do it?)

1. If my water should maintain a K2SO4 level between 10-20ppm, and the recommended dose is 1.67 mL, which will raise the level by 3.33ppm, how fast should I bring the water up to that level?

2. How can I safely do that without hurting the plants (real world)?

3. How do I calculate for consumption?

I feel that dosing K2SO4 is more challenging due to the fact that there are no freshwater tests available for determining K2SO4 levels.

Note: I am using RO water that I buffer and control GH. I mention that because water changes alone will not add any K2SO4 to my aquarium.


Noteworthy: (from my research):

Benefits: Potassium helps regulate plant metabolism and affects water pressure regulation inside and outside of plant cells. It is important for good root development. Potassium treats for leaves yellowing, browning, pinholes, weak stems & roots.

Deficiency Symptoms: Brown scorching and curling of leaf tips as well as chlorosis (yellowing) between leaf veins. Purple spots may also appear on the leaf undersides. Plant growth and root development are usually reduced.

Notes: There is no level at which potassium becomes toxic to plants. But when plants get too much potassium, the absorption of other nutrients is inhibited, which leads to the symptoms caused by the deficiency of those nutrients. (That is a biggie!) It means that if you overdose potassium, you may think that apparent deficiencies with your plants are being caused by not dosing enough of the other ferts. Where in reality the problem is that you are overdosing potassium! Wow, I'm glad that I looked that up!

Ok, thank you for reading. Much appreciated.

~Chip
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Last edited by Chip Munk; 11-17-2016 at 09:49 AM. Reason: Add question
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post #2 of 11 (permalink) Old 11-17-2016, 02:10 PM
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What else are you dosing, how much, how often?

If you haven't already you should look into different dosage methods. The main ones are PPS and EI. EI seems to be the more popular here. Basically daily dosing of ferts providing the plants with a little more than they can use and then resetting the levels once a week with a 50% water change. Take a look at the stickies in the fertilizer section.https://www.plantedtank.net/forums/11...eters-faq.html Lots of good info there to get you going.
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post #3 of 11 (permalink) Old 11-17-2016, 04:23 PM
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1. Using EI, you can just dump the whole dose in. The fish don't like it when you do, but they tolerate ok.

2. With Estimative Index (EI), you flush out the tank by changing some of the water, removing some of the remaining ferts and add another dose of ferts. Once a week, and EI requires 50% water change.

3. See 2. There are recipes for EI ferts here on the forums https://www.plantedtank.net/forums/11...n-recipes.html and I use 1/4 Nico something sells dry ferts for mixing up.

Oops - I did a member search for nico and didn't find him. I hope the post is still there.

MY TANK: Planted 10g; 2 x 10W CFL; Fluval U2 internal filter; MGOCPM/black sand cap

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post #4 of 11 (permalink) Old 11-17-2016, 07:11 PM
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post #5 of 11 (permalink) Old 11-17-2016, 09:35 PM
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K is not typically a problematic nutrient. I have had 20,30,40,60,80 and 100+ K ppm levels in my tanks with no issues. The highest I did was 150 ppm K and this was tested by a laboratory. On Average, I keep my K levels around 40-60 ppm (high tech tank) and not worry about it too much. Usually if the Ca/Mg levels are higher then I try to keep my K higher too. Like what Django suggested, you can dose for the target K after a water change and forgot about it.

Typically the K levels will get higher if you are dosing KNO3 and KH2PO4.

There are also freshwater K tests that are available. Unfortunately they are very expensive and not worth the money unless you own multiple tanks.

Potassium Portable Photometer - HI96750 - Hanna Instruments

Benchtop Multiparameter Photometer for Water Analysis - HI83200 - Hanna Instruments
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post #6 of 11 (permalink) Old 11-18-2016, 01:37 AM Thread Starter
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Hello Kubla,
I'm revisiting that after reading a Tom Barr post.

Bump: Thank you PortalMasteryRy,
I hear ya. And that $900 meter would make a great stocking stuffer. :-)

Looks like I have some lighting to buy.

~Chip
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post #7 of 11 (permalink) Old 07-18-2019, 07:44 AM
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hi. I have question about K.. i tried EI 3 times and always had problem with melted top of the plants.. with GH around 5. it always was too high potassium around 20ppm. i Used K only from kno3. circulation was good, Degassed tank was 7.8ph with co2 on was 6.2ph lights was ok. ferts: NO3 30ppm, K 20PPM, po4 3PPM. micro 0.5ppm Fe. where is the problem? still to low CO2?
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post #8 of 11 (permalink) Old 07-18-2019, 02:50 PM
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Generally plants need more nitrogen than potassium. So if you are dosing to 10ppm NO3 with potassium nitrate and 1ppm PO4 with potassium phosphate you should have more K tan you need. The primary reason to add potassium sulfate is not to increase potassium, but to increase sulfur. Sulfur is a macro nutrient that plants need.

Quote:
Note: I am using RO water that I buffer and control GH. I mention that because water changes alone will not add any K2SO4 to my aquarium.
If you are using a sulfate GH booster you already have enough sulfur in your tank. Adding potassium sulfate in your case is not necessary. Sulfate GH booster such as Seachem Equilibrium use the ingredients calcium sulfate (Gypsum) and Magnesium sulfate (Epsom salt). Other GH formulas on the market are chloride based made by mixing calcium chloride and magnesium chloride.plants don't need a lot of chlorine (it is a micro nutrient). Many people just buy the ingredients and make there own GH booster.

Additionally many GH boosters on the market include potassium even through it is not detected by the GH test.
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post #9 of 11 (permalink) Old 07-18-2019, 03:32 PM
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Quote:
Originally Posted by Pulsar View Post
… it always was too high potassium around 20ppm… ferts: NO3 30ppm, K 20PPM, po4 3PPM. micro 0.5ppm Fe. where is the problem?
Water column 20 ppm of K is not high, it is rather medium low. The NO3 30 ppm, PO4 3 ppm, K 20 ppm and Fe 0.5 ppm are water column concentrations?
Quote:
Originally Posted by PortalMasteryRy View Post
K is not typically a problematic nutrient. I have had 20,30,40,60,80 and 100+ K ppm levels in my tanks with no issues. The highest I did was 150 ppm K and this was tested by a laboratory. On Average, I keep my K levels around 40-60 ppm (high tech tank) and not worry about it too much. Usually if the Ca/Mg levels are higher then I try to keep my K higher too. Like what Django suggested, you can dose for the target K after a water change and forgot about it.
Thanks for sharing, it is very helpful in the era of potassium hysteria.


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post #10 of 11 (permalink) Old 07-18-2019, 04:43 PM
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Quote:
Originally Posted by Pulsar View Post
hi. I have question about K.. i tried EI 3 times and always had problem with melted top of the plants.. with GH around 5. it always was too high potassium around 20ppm. i Used K only from kno3. circulation was good, Degassed tank was 7.8ph with co2 on was 6.2ph lights was ok. ferts: NO3 30ppm, K 20PPM, po4 3PPM. micro 0.5ppm Fe. where is the problem? still to low CO2?
Sounds very close to my tap and tank parameters kh=5, gh=8 tap ph=8.0 and I drop it to 6.5. I had trouble with EI ferts as well but its very plant species specific and how heavy you plant. I don't think its specifically the K, but it could be too much Fe or many other things. I find I get Algae if I increase N even past 10ppm but that is with my low plant mass (see my signature).

Don't listen to the nonsense about not enough CO2 if you have a 1.6ph drop and reasonable amount of light its unlikely to be that unless you have flow issues.

It depends on the plants but if you have Lythraecae like Rotalas or Pogostemon Erectus or similar family they likely won't like that heavy ferts in hard water.


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post #11 of 11 (permalink) Old 07-29-2019, 11:12 AM
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Level of K depends from Gh. I know that you can have in hard water potassium on 80ppm but in soft water is a little bit diferent Tom Barr has in soft water GH3 concetration of K 40ppm with no issue. i think i did something wrong and potassium around 25ppm concentration in the tank did disaster.. i'ts not high Fe or micro. with Fe 0.3 i had the same efect. so i'm looking the source of the problem. not enough Co2? or light.. i have Led 26W but i think maybe change on 4x 24W T5 on 63liters.
Concetration in tank i have right now Gh6, Kh3, Ca30ppm, Mg 7ppm, K 7ppm, NO3 30ppm, Po4 2,5ppm
i'm useing iron gluconate so i can't measure Fe. i thing is around 0.3ppm. Ph was 6.3 now i have 5,8.
My Plants :
Tonia Belem, Giant, Madeira, Fluviatilis , Erios several types, Pantanal. mostly the harder stem plants.
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