Calcium is an interesting nutrient because while it’s very important, plant uptake is very passive. Basically, plants take up calcium as they take up water. While plants actively take up other nutrients, calcium uptake is limited by the concentration of calcium in the solution and by how much water the plant takes up.

1. Calcium in Aquaponics
Calcium in Aquaponic Systems – A Very Important Nutrient
Calcium is one of the most important plant nutrients- in fact there are some who argue that
it should be one of the primary plant nutrients, up there with nitrogen, phosphorus and
potassium.
A Common Nutrient in Aquaponics
Make sure to watch the video on Calcium!
The fact that this is debated speaks to its importance in the plant growth cycle. Calcium is a
common nutrient in aquaponic systems and is not usually deficient due to pH (although if you
run very low pH, it can impact availability!).
Most water is fairly hard, so calcium enters the system every time the grower tops his system
off in the form of calcium carbonates. In healthy systems, these carbonates are quickly
consumed, leaving the calcium for plant uptake.
Calcium Up Take is Passive
Calcium is an interesting nutrient because while it’s very important, plant uptake is very
passive. Basically, plants take up calcium as they take up water. While plants actively take up
other nutrients, calcium uptake is limited by the concentration of calcium in the solution and
by how much water the plant takes up.
This is important to understand, because with some crops calcium deficiencies have nothing
to do with concentrations, pH or any of the common deficiency culprits.

2. Sometimes calcium deficiencies occur simply because your crops are not well ventilated, and
humidity is too high. This means that the plants are not transpiring (losing water through
their leaves) very much, which means that they aren’t taking up much water, which means
that they aren’t taking up enough calcium.
Signs of Calcium Deficiency
It’s important to know what you’re looking for when it comes to calcium
deficiencies. Calcium deficiencies in some instances can imitate Potassium and Magnesium
deficiencies, with the chief difference being black, dead areas of young and growing plant
tissue. (Because Calcium can imitate other deficiencies, use a key to diagnose!)
Usually, this is apparent at the growing areas at the top of the plant. The young tissues die
first because plants aren’t very good at transporting calcium within the plant. It is one of the
elements that are immobile in the plant. This is because calcium is often used as a kind of
structural material, helping to hold together cell walls. For this reason, calcium is a lot like
cement. Once it’s been used, you can’t really move it and reuse it.
Have you downloaded our free nutrient deficiency key yet? Click to download.
Treating Calcium Deficiencies
If you’re certain that you’re seeing a calcium deficiency, you have a few treatment options.
If you want to balance your system Calcium in solution, you should look into hydrated lime
additions (low pH systems), calcium carbonate (very low pH systems), chelated calcium
additions, or foliar applications of calcium chloride.
The Best Treatment Option (in our opinion)
Calcium chloride foliar applications are the best way to supplement calcium and see results
quickly. I typically recommend around 1 tsp/gallon of water to start.
Caution: Salt Alert
The same caution applies to calcium chloride as it does to potassium chloride- you are
applying a salt, so apply carefully in very low volumes early in the morning or preferably, at
dusk. Remember, when doing foliar applications, it is always better to apply low
concentrations more frequently than to apply higher concentrations with less
frequency. Caution is always recommended!
Other Treatment Options
For these other supplements, dose based on your system pH. Here at Bright Agrotech, we
use a lot of hydrated (or “agricultural”) lime as well as potassium hydroxide to raise pH. This
naturally supplements calcium as the pH is moderated.

3. If your system has a neutral to high pH, then chelated calcium can be a great way to get
calcium to your plant roots. The amount you add will really depend on your particular
system.
If you have the means to test calcium in your aquaponic systems, you should be shooting for
at least 40-70 ppm calcium (with other nutrient levels at recommended levels! See other blog
posts.).
If don’t have the means to test calcium, then regular calcium dosing at low levels (i.e. to
control pH within a certain range) is unlikely to hurt your system. Your system will tolerate
relatively high levels of calcium, but high levels (in aquaponic systems 120-150 ppm +) can
begin to interfere with uptake of other nutrients.
Note: This is only for aquaponic systems. Hydroponic systems can tolerate higher
concentrations of calcium in solution since the solutions are typically better balanced in
regards to other plant nutrients. For more information, visit
http://verticalfoodblog.com/calcium-in-aquaponics/