Backyard Aquaponics
A place to discuss aquaponics

I searched the prior post for references to using eggshells to provide calcium in the AP system, but the solutions seem unclear.

Reading general posts, it seems insufficient calcium seems to be a frequent problem, especially with tomatoes. In my dirt garden, I add eggshells to tomato pots when I start them, as well as, regularly in my compost pile.

Is it a good idea to add them to the AP system overall, the GB for the tomatoes (but the water will spread system wide), or wait till there is a problem?

I know that by the time the garden tomatoes show a calcium deficiency, I've lost my production for the season. I'd like to avoid this in the winter AP system I will start building next week.

How do you provide calcium in your systems? Note: I'm raising tilapia in my system.

Thanks for any ideas, Pat

what is your pH. Simplest if you have an acidic system (around 6.5 to 7) is to alternate between CaHCO3 and KHCO3.
That will work with the acidity and provide both Calcium and Potassium.

Shells are probably more effective than egg shells. Either way it probably wont add much Ca to the system.

If you have a high pH system then it is a bit more problematic. You probably best to go with foliar feeding.

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personally I find that tomatoes need a bit more attention than other veg.
So I tend to feed direct onto the grow bed (in my case dutch buckets).
I also add blood&bone with potash* around the base of plant and water it in so it acts as a slow release.
Our town water has Calcite buffering (Calcium source) and I buffer for acidity in winter so I don't get Ca issues.

* that is an Australian product but you will have something similar or can make it up yourself.

I too had an issue with calcium in my first system with tomatoes. I went with adding crushed oyster shell in my FT. I also amended with bone meal at the root site. I don't know what had more of an impact but both seemed to make a difference. I also added epsom salt every now and then to the system.

My recommendation instead of trying to narrow down a specific nutrient, is to sort them all out, if one thing is lacking, another is probably close behind. Look for something like seasol powerfeed:

http://www.seasol.com.au/products/62/PowerFeed

Or the American equivalent, it's a seaweed extract (read up on what's in the others though, too much zinc/copper and don't use it). If you add too much of one nutrient, it can lock out another, and make other issues.

Eggshells take forever to breakdown on their own.
Can save your eggshells, roast/brown (not black) them then add 4 parts brown rice vinegar and leave for a day or so. The vinegar breaks down the shells and supposedly the calcium becomes water soluble. The vinegar certainly tastes chalky when you are done but I don't know for sure if the calcium itself is plant available.