Potassium in Aquaponics

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Potassium in Aquaponics:  N-P-K

Potassium is hands down the most interesting and frustrating nutrient to manage in aquaponic systems.

When there is a nutrient deficiency in aquaponic systems, 9 times out of 10, it is a potassium deficiency.

Not only is there typically a lack of adequate levels of potassium in fish feed and waste, but potassium has a rather complicated relationship with other nutrients in the system.

For this reason, I’m going to cover the topic of potassium in a series of several posts, including:

1. An Introduction to Potassium

2. Potassium In Your System

3. Potassium Deficiencies- Recognizing Them and Why they Occur

4. How to Treat Potassium Deficiencies and How to Manage Potassium to Prevent Deficiencies


An Introduction to Potassium *

Potassium is introduced to your system in the form of fish feed or supplements like Potassium Hydroxide, or Kelp Meal Concentrate.

Unlike many other plant nutrients, Potassium does not occur at high enough levels in most fish feed to supply adequate amounts of potassium to both your fish and your plants.

This means that potassium is often deficient in aquaponic plants (if potassium isn’t supplemented).

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Potassium in Aquaponics *

Potassium is a fairly simple, soluble element in your system.

potassium in aquaponicsIt is an important element for plants as well as animals.  In fact, almost all life on earth needs potassium to survive.

Because it’s simple, soluble and charged, potassium is an important signaling ion, as well as a very simple and effective ion to control the osmotic potential of plant cells.

Basically, the plant uses tiny pumps to move potassium from one area to the next in order to “inflate” those cells with water.  Water moves from the cell with low potassium concentrations to the cells with higher concentrations.  This allows the plant to keep it’s tissues full of water, which is important since plants are mostly made of water.

It also allows the plant to do things like open tiny ports in the surface of the leaves (called stomates or stomata) to allow gas to enter and leave the plant leaves. It’s also a signaling molecule, meaning that the plant uses potassium to communicate between the different cells and parts of the plant.  This helps plants grow and reproduce effectively, as well as mount defenses to diseases and pests.

Potassium deficient plants are more susceptible to pests.

Last but not least, potassium is also very important to the protein making process, and without proteins, plants cannot survive.

Fish also need potassium, and it’s typically in the top 10 most important elements (by % of bodyweight) for growing fish.  For this reason, fish feed usually contains quite a bit of potassium.

Unfortunately for aquaponic growers, feed is formulated to be efficient- which means not including much more potassium than is necessary for the fish.  In traditional aquaculture, in the best case scenario, excess potassium in the feed just goes to waste.

In the worst case scenario it can lead to other problems in the system.  This means that when traditional aquaculture feeds are used in aquaponics, there just isn’t usually enough potassium to go around. For this reason, potassium must almost always be supplemented in aquaponic systems- which brings us to the heart of the matter. . .


Check out the first Potassium video:

Potassium in Your Aquaponics System (Part 2) *

Learn what potassium looks like in your system.

Click here for part 2.





  1. Good to see someone addressing the inter-relationship between Potassium, Calcium, Magnesium… look forward to the rest of the videos

  2. Very good. Cant wait for part 2.

  3. Thank you Nate for breaking this subject down

  4. Thanks Nate. Finding out all sorts of info. Wish I had more time and mney to get things going.

    • Hi James! Glad to hear you’re finding this info useful. I think we can all agree on needing more time and money in life!

      Hope 2014 is good to you.


  5. Thank you Nate, You have been making some really impressive videos. I like the way you make it easy to understand the basics and still impart some technical knowledge along the way. Looking forward to the next video.

  6. How much and how often do you add kelp meal (0-0-10) and/or potassium sulfate(0-0-50) to your system. Thanks for any reply.



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  3. Diagnosing Potassium Deficiencies in Aquaponics - Bright Agrotech - […] Part #1) Introduction to Potassium […]
  4. Magnesium in Aquaponics - Bright Agrotech - […] and Magnesium is a very important plant nutrient and is up with Potassium when it comes to common plant …
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