How To Make Eggshell Powder.

Eggshell powder can be use to raise the system pH whilst adding calcium. It also contains magnesium and some trace nutrients.

  • Author: Paulo Marini.
  • Time required: 90 minutes.
  • Difficulty: Very easy.

Authors: LEMOS-MARINI, P. CARIGAN, P. 2014.


Aquaponics has a natural tendency of pH lowering with time, as the processes of decomposition, mineralization and nitrification releases hydrogen ions into the water. And it also presents nutrient deficiency, especially in regards to calcium and potassium.

To counter-balance this process, maintaining pH stability at an optimal level for plants and aquatic animals requires the addition of hydroxides or carbonates. A range of products can be use to control pH and supplement the lacking elements, such as:

  • Calcium carbonate.
  • Calcium hydroxide.
  • Potassium carbonate.
  • Potassium bicarbonate.
  • Potassium hydroxide.

Explanation of the Technique

This guide describes how to obtain calcium carbonate from eggshells by heating them (to eliminate the risk of E. Coli contamination), and then by transforming them into powder – it’s important to transform the eggshells into fine powder to increase the surface area and raise the rate of dissolution. The idea is not novel, but the authors have refined the technique, tested it in real conditions, and documented it.

Benefits of the technique

The benefit of using eggshell powder instead of hydroxides and industrial grade calcium carbonate are:

  • Use of a extensively available waste product at low or no cost.
  • Safety in regards to the first.
  • Preventive supplementation of a broad spectrum of trace nutrients.


We have established, empirically, that a mixture weight of 50% egg shell powder and 50% potassium bicarbonate is the ideal combination to control pH, while adding necessary calcium and potassium elements for the conditions of the AquaGarden System.


  • Oven.
  • Coffee Grinder.
  • Ovenware.

Relevant Parts:

  • Container – Sealable.

Step 1

  • Collect a tray full of eggshells.

Step 2

  • Place it in the oven for one hour at a temperature of between 150c to 180c.
  • This will sterilize any micro-organisms and dry the eggshells.

Step 3

  • Crush the eggshells.

Step 4

  • Use a coffee grinder to turn them into a fine powder.

Step 5

  • Fine powder appearance.

Step 6

  • Store in sealable container.

I've done it! Success!

Now onto the next task.