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Does potassium nitrate (KNO3) provide the full EI levels of potassium (K)?

xZaiox

Member
Joined
31 Mar 2022
Messages
155
Location
Maidstone, UK
Hi guys,
Sorry if this is a silly question, but I'm having some issues in my tank and I've decided to review what I'm dosing and I'm now thinking I may be underdosing potassium. I copied the below table from a post of @Zeus. that I found in a past ukaps post. Everything I have read has indicated that the potassium from dosed KNO3 will be sufficient. I've been dosing to roughly Clive's EI target - I've been dosing 22.5 ppm NO3, and putting this into the rotalabutterfly nutrient calculator, this equates to 14.19ppm of K. When also factoring in the 3ppm weekly dosage of PO4 from K2PO4, the calculator says this provides 2.47ppm of K.

So if this calculator is correct, then I am underdosing potassium by nearly half. Does this information sound correct? Because if so then I think I will try adding some K2SO4 to boost the levels to 30ppm.

I guess I'm confused by this because surely if the calculator is correct, then EI recipes should also include K2SO4?

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plantnoobdude

Member
Joined
17 Mar 2021
Messages
1,072
Location
uk
Hi guys,
Sorry if this is a silly question, but I'm having some issues in my tank and I've decided to review what I'm dosing and I'm now thinking I may be underdosing potassium. I copied the below table from a post of @Zeus. that I found in a past ukaps post. Everything I have read has indicated that the potassium from dosed KNO3 will be sufficient. I've been dosing to roughly Clive's EI target - I've been dosing 22.5 ppm NO3, and putting this into the rotalabutterfly nutrient calculator, this equates to 14.19ppm of K. When also factoring in the 3ppm weekly dosage of PO4 from K2PO4, the calculator says this provides 2.47ppm of K.

So if this calculator is correct, then I am underdosing potassium by nearly half. Does this information sound correct? Because if so then I think I will try adding some K2SO4 to boost the levels to 30ppm.

I guess I'm confused by this because surely if the calculator is correct, then EI recipes should also include K2SO4?

View attachment 193420
Technically yes, you are “under dosing” potassium. In the real world? Not even close, no tank will ever need 30, 40, 50 ppm potassium. (Levels you will reach with accumulation.)

Just dose your KNO3 and call it a day, no need to complicate it. For what it’s worth, my tank (heavily planted full of stems with high light and co2) gets 4ppm potassium at water changes, Target dosed Every few weeks. And in between water changes, they get only 0.6-1.3ppm K weekly.
 
Last edited:

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
4,633
Location
Yorkshire,UK
As @plantnoobdude said you are unlikely to need 30ppm K, this is the EI level of abundance for high light ,CO2 and lots of plants ie Dutch style planted tanks. Plus if using tap water you will be getting some from there as well. If you plants look good then all is OK. If plants not so healthy K2SO4 is a very cheap way to boost your K levels. Got mine from E-bay.
 
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