Potassium in Your Aquaponics System (Part 2)

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Potassium in Your Aquaponics System

Potassium is almost always deficient in mature aquaponic systems unless it is supplemented. Plants, and especially flowering and fruiting plants, consume potassium at rates significantly higher than rates of input. This basically means that in order to have healthy plants, you’ll have to artificially bump up the amount of potassium in your system.

Miss part 1?

Read the Introduction to Potassium here.

Supplementing Potassium in Your System

You can do this one of two ways- by adding potassium to your system solution, or by applying it foliarly (spraying it on the plant leaves).

Adding potassium to your solution is often the easiest way to supplement potassium, but it can also be problematic.  This is because the amount of potassium you add to your system isn’t always what is available to your plants.

Potassium is being consumed by other organisms in the system and is often reacting or interacting with other elements in ways that we don’t expect.  This means that our plants can show potassium deficiency symptoms, even if there is technically plenty of potassium in the system.

Potassium’s Relationship Status: “It’s Complicated” *

Potassium has a complicated relationship with other elements- namely Calcium and Magnesium (both very important nutrients in their own right!).

potassium in aquaponics

Dr. Nate Storey discussing potassium in your aquaponics system.

Calcium is the primary nutrient that complicates potassium in many systems.

It is very common in aquaponic systems to use calcium carbonate to “buffer” pH, and even where it isn’t common, there are many areas where water is hard with calcium based carbonates.  This means that calcium is entering the system in the form of fish feed as well as calcium carbonate.

While calcium can be deficient in many systems, there are a few where it is abundant to the point that it impacts potassium availability. This means that when there is lots of calcium present, it can reduce a plants ability to take up enough potassium, leading to deficiencies.  The same is also true of magnesium, but to a lesser extent.

Seek a Balanced Aquaponics System *

So, it is important to maintain a balance between these three contenders if you wish to supplement potassium effectively.  We must make sure that we are not supplementing one at the expense of the others.

There are two ways to accomplish this:

  1. Balancing inputs (maintaining a balance between Potassium, Calcium and Magnesium additions based on your system’s needs)
  2. Applying one, or all of these nutrients foliarly (essentially bypassing much of the issues with trying to balance nutrients in solution).


Are You Ready for Part 3?

Read part 3 here

potassium in aquaponics




  1. Hey Nate does organic potash contain potassium?
    I used a product in my grow beds recently called azomite. Its primary use is in land farming. It is omri certified so I thought it would be great natural supplement to add trace elements and minerals in my system. Unfortunately i made a newbie mistake and didn’t think through how the calcium content would afeect my pH. My tap water is 6.8 but since adding the azomite my pH is 8. I have tried to bring it down artificially but within days it is back up to 8. My question is will my plants be able to take up the available mjnerals at pH8? Will adding FeEDDHA assist the plants taking up other minerals also?
    Azomite is an annual application so i believe it will gradually leach into my system ovrr the next 9-10. Is there anything I can do to bring & keep my pH down or help my plants take up the available nutrients whilst the pH is so high?
    Cheers mate.

  2. Love the vid(s) Nate. I’ve been treating my high ph system with potassium sulfate – so was good to see this on the key that came with the vid as well – the increase in growth is very noticeable. The Key says in low amounts – what is low? I’ve been adding 1 tsp per 1000L though is this too much? Would there be a problem with build up of sulfates? When will zipgrows be available in Oz :) ?

    • Hey Matt! You can find ZipGrow towers in Australia right now at http://growpacked.com/site/shop. 1 tsp per 1000L isn’t too much. You’re smart to bring it up slowly! We would love to see photos of your ZipGrows in action when you’re all setup, Matt.

  3. We’re using potassium bicarbonate at the rate of 20 grams per 1000 litres, this seems to raise the potassium by about 10 parts per million and keeps the pH above 6 because the tap water we use here in north Brisbane Australia is quite soft.

  4. Hi Dr. Nate, I have watch all your videos in youtube, they are great! I found on your blog that the right concentrations are: Calcium 40-70ppm, phosphorus 10-20/20-40ppm but I can’t find the ideal concentration of potassium (Never added) and Iron (currently 2-3ppm of DTPA). My system ph is 7.4 and I was going to add Potassium Bicarbonate but after your videos does not seem right. Should I add potassium Chloride? Thanks for your time!



  1. Diagnosing Potassium Deficiencies in Aquaponics - Bright Agrotech - […] Part #2) Potassium in Your System […]
  2. Comment on Potassium in Your Aquaponics System ... - […] Hey Matt! You can find ZipGrow towers in Australia right now at http://growpacked.com/site/shop. 1 tsp per 1000L isn’t too …
  3. Aquaponics Resource Guide - Bright Agrotech - […] Potassium 2 […]
  4. Potassium in Aquaponics: A Helpful Overview - […] Click here for part 2. […]
  5. Diagnosing Potassium Deficiencies in Aquaponics - […] Part #2) Potassium in Your System […]

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