homemade calcium?

Is there anything easily found at home to increase calcium? Heard crushed eggshells work. Any others?

crushed egg shells are slow release and can only be used in soil. you can make calcium acetate or calcium sulphate by adding either vinegar or sulfur acid to create one of those polar molecules. those can be dissolved and are readily available by plants. i usually add 150ppm of one of those in my hydro res as a aqueous solution. alternatively you can add calcium nitrate i guess.

You can use eggshells in coco and soilless mixes as well. I know someone that uses eggshells in coco to achieve some stunning results.