Aquaponic Deficiencies ~ Get past the yellow and see more GREEN.
Since the obvious goal of gardening, whether for pleasure or profit, is to produce a quality product within the least amount of space possible with only a minimal amount of work; then it only stands to reason that we should offer our garden the best possible chance for success.  In organic gardening, we must be careful of our choices, but in Aquaponics even more so.  We are not only striving for these goals but creating a miniature ecosystem wherein we have a secondary means of product – BACKWATER-DIY-Quarterly-Articles-22FISH!  In this carefully designed system, we limit ourselves to not only organic standards, but we must also safely manage the health of our fish.

Many Aquaponic gardeners struggle with maintaining the necessary critical levels of highly usable forms of Calcium, Phosphorus, and Iron since these are either minute or missing entirely in the nutrient-rich effluent. How much and how often the addition of these nutrients is necessary is a constant topic. Without them, you will most likely be missing out on how productive your Aquaponic garden can be, but the answer to the question is not set in stone.

Since the need for these nutrients depends on what you are growing, your necessary inputs may likely change thru the season.  In any case, we still must adjust standard garden practices for safe and fish friendly products to correct the deficiencies. In the end, if we can provide natural and effective means of these elements, then the outcome is always a sweet success.

So the question then becomes, What is safe for Aquaponics? For both the beginner and the seasoned Aquaponic gardener if these items should be in your arsenal. Calcium in limited amounts also plays a role in the general growth and development of the plant as well as the ability of the fruit to form correctly and maintain a stable cellular structure after harvest.


  • Coral Calcium in Liquid or Powdered form tops the list for easily absorbed Calcium.
  • Oyster Shell or Chicken Grit will provide a slow release form of Ca+.
  • Calcium Carbonate or Agricultural Lime (Careful, this will buffer your PH quickly).
  • Composting worms in your system creates a living source of Ca+ thru their castings.
  • Phosphorus – Spindly or thin stems and stunted growth are the first signs of phosphorus deficiency, later veins and/or leaves may appear purple or bluish green.  Without phosphorus, you will have limited capacity for the plant to produce its fruit.
  • Greensand is a slow release a form of Phosphorus along with micronutrients which can be added to your beds.-Banana Peels which are broken down by your friendly composting worms into a highly useable form of Phosphorus in their castings.
  • Bone meal, Rock Phosphorus, and Food Waste Compost,  as well as Unsulfured Black Strap Molasses, used as a foliar spray made in the fashion of an aerated compost tea spray, are high in Phosphorus and will both combat insufficiencies and promote blooming.
  • Iron – Although it is an uncommon deficiency in the soil, in Aquaponics iron is more likely unavailable due to an improper PH (5-6.5 is necessary for iron to be available with the optimum ph of 6-6.5). In addition, high amounts of other elemental nutrients (Calcium, Manganese, and Phosphorus) can possibly tie iron up and result in the same deficient markers.
  • Chelated Iron in liquid and powdered forms are the major sources of naturally available soluble iron. The occasional handful of Greensand will provide a slow release form of iron.
  • Unsulfured Black Strap Molasses as a foliar spray or in a compost tea spray supplies bio-available iron directly to the plant.


Written by: Catherine Billings of Backwater Provisions Co. June 8, 2011

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