nitrogen needs to be converted to a more useful form by the nitrifying bacteria (J.D., 2006). The process
is very slow, the best experimental results show the conversion to nitrates at 1.14 mg per minute per
gram of bacteria present in solution (Lena, 2001). Increasing the amount of fish would serve no purpose
if the levels of bacteria is not also proportionally increased, here a tradeoff presents itself. The levels of
fish and bacteria can be increased to grow fruiting plants, but the heightened levels of bacteria inside
the system increase the risk of eutrophication, which is detrimental to the fish. These factors will be
carefully considered in selecting the plants for growth, the types of plants will serve as a measure of
how much fish is needed to effectively sustain the plants.
The following table is list of plants that have been grown using aquaponics, and are classified by the
optimum levels of nitrogen needed for growth. Three levels of nitrogen concentrations of low,
intermediate and high were used to classify the plants according to their requirements needed for
optimal growth.
Low (25.0-
35.0 kg
N/ha)Intermediate
(35.1-50.0 kg
N/ha)High
(>50.0 kg
N/ha)
Leafy Lettuce cucumbers Tomatoes
Pak Choi Squash Peppers
Kale Broccoli Beans
Swiss Chard Cauliflower Legumes
Arugula Cabbage
Basil
Mint
Watercress
Chives
Table 12. Nitrogenous requirements of Plants Commonly Grown in Aquaponics
Other plants that can be examined, and can be grown through aquaponics are; herbs, and flowers.
Though not listed in the above table herbs generally require a lower amount of Nitrogen than flowers.
Flowers Woody flowering species for cut flower production, such as forsythia, pussy willow and
flowering cherry, need at least 48 kg of nitrogen per hectare for optimum growth. (Nutrient
Recommendation For Commercial Cut Flower Production, 2009) The creation of pigments, and
reproductive plants in flowers require larger amounts of nutrients, as these flower heads are sometimes
the precursors to fruits. Herbs on the other hand can flourish under conditions where the nitrogen is
below 25 kg per hectare. The smaller size of the herbs, requires less nutrients to develop, hence less
nitrogen is needed during germination. (H. & Hendawy, 2009)
2.3.3.1 Seedlings
A seedling is a plant that is in early stages of development. Seedlings cannot use photosynthesis to
create food and the necessary energy needed for them to survive. As a result, seedlings are dependent
on the source of nutrients that they receive from the seed. Seedlings are usually grown in a greenhouse
or another indoor medium before they are transplanted from these areas to outdoor environments.
(P.H., 2005) This is very beneficial to the seedlings, as during the very early stages of development,
seedlings are prone to attack by pest and disease. The protected environment inside the greenhouse
greatly increases the chances of survival until the time for transplanting. (Buczacki, 1998) The best time