egg-12We eat nutritious plants, but the plants need a starting place for their nutritiousness! Well, here at Aquaponics Magazine we live in the spirit of the DIYer.  With that said, let’s start with a quick overview of plant nutrients.


We are all familiar with fertilizers from the store with printed numbers like 20-20-20 on the front.  And maybe, one might even know the numbers stand for the N-P-K or the nitrogen-phosphorous-potassium concentration of the fertilizer.  Fertilizers are labeled in this manner because plants require these nutrients in large quantities, or macronutrients.  Interestingly, there are 3 lesser known macronutrients: magnesium (Mg), sulphur (S), and calcium (Ca).

Aside from Potassium, Calcium may be one of the hardest nutrients to provide our plants in Aquaponics.  There are a collection of calcium supplies offered in the marketplace.  The most prevalent varieties include calcium nitrate, calcium chloride or calcium acetate (Tourte, & Faber, 2011).  Most of us are searching for organic solutions or at a minimum fertilizer, solutions to supplement the plants that won’t harm the fish or bacteria.  So, how do we do this?

Method to My Madness

There are plenty of ways to add calcium to your system, but I would like to propose an inventive solution that is empowering by giving you control of the fertilizer-creation process and best of all, it€™s cheap!  This method is organic, but some may have slightly different opinions.


Relevant chemical reactions: CaCO3 + 2CH3COOH = Ca (CH3COO)2 + CO2 + H2Oegg-22

Materials Needed:

Eggshells (cleaned)

Table vinegar, clear and distilled (3-5% acetic acid)

Small container

First, clean and crush some eggshells. The more you crush them the faster they will dissolve, but don’t worry about crushing them into a fine dust. Just crunch them in your hand a few times, this is enough.

Alternatively, you can use old seashells, clamshells, or oyster shells, but the amount of vinegar will be different and it’s a lot harder to crush some of these meaning they will take longer to dissolve in some cases.

Now, for every eggshell use 1 cup of vinegar. Pour the vinegar into a container, preferably glass. Add the eggshells and let it sit for 24 hours. When you return, the eggshells should be completely dissolved. If they are not, add 1/4 cup of vinegar per egg. egg-32Eggshells can be very different sizes and densities. Once it has fully dissolved, pour the solution directly into your grow bed or fish tank. Add a maximum of 1/4 cup of this solution per 100 gallons of water in your system. If you have a very large system, just add what you have and monitor your plants. The calcium carbonate and acetic acid will create calcium acetate.



Tourte, L, & Faber, B. (2011). Small farm handbook (2nd ed.). Oakland, CA: ANR Publications.

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