Why hard tap water can be good for your plant: A hydroponic fertilizer study

In the past my usual solution of 15-30-15 Fertilizer and Epsom salt has been sufficient when mixed with tap water.

In my latest build, I did the same blend of nutrient solution for my plants, but I began to notice slight tip burn on my bok choy and lettuce. The first few days wasn't concerning, but since it started appearing on all the bok choy within time, I decided to do some research.

Yellowing of the leaves

Calcium is one of the main nutrients used by plants to hold the cell walls together. When deficient, the cell walls collapse, causing the leaves to grow deformed.

For my previous hydroponic projects (See here and here), the tap water supply from both cities was notoriously hard to the point of being famous. The calcium concentration of the water was more than double of that from the tap supply in my new town.

So what's the best way to increase the Calcium concentration in my reservoir? I needed a source of soluble Calcium. Luckily from some research online and previous experiments way back, I knew eggshells were a reliable source. Acids break down the Calcium Carbonate found in eggshells into a more soluble Calcium salt (i.e. Calcium Citrate, Calcium Acetate, Calcium Nitrate, etc)

The easiest acid available to me at the time was Acetic Acid, in the form of distilled white vinegar. I located a very simple instructional video on how to synthesize Calcium Acetate from eggshells and went to work.

Making the solution of Calcium Acetate was very simple. I took some used eggshells, dried them in the microwave at about 30% power, and then added them in excess to a bowl filled with vinegar.

The solution began to bubble and fizz calm instantly after adding in the egg shells. I allowed this solution to mix and sit for a few hours before filtering off the liquid. Unlike video, it makes more sense to keep my Calcium Acetate in solution as I will be mixing it into the liquid reservoir.

Better living through chemistry!

Running the math, as long as this solution is fully saturated, approximately 1/2 teaspoon of the Calcium Acetate solution is enough to bring 1 gallon of my nutrient solution to the Calcium concentration of my previous water districts.

This ended up being successful as the Bok Choy eventually recovered and no longer exhibited deficiency in their leaves. Who knew that my college degree would help me with something in life!

How the Bok Choy ended up a few weeks later

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