Aquaponics is the integration of aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks) with hydroponics (cultivating plants in water) in one production system. Water quality also play an important role in aquaponics system.
In an aquaponics system, water from an aquaculture system is fed to a hydroponic system where the fish wastes are broken down by nitrifying bacteria initially into nitrites and subsequently into nitrates, which are utilized by the plants as nutrients, and the water is then recirculated back to the aquaculture system. This process allows the fish, plants, and bacteria to thrive symbiotically and to work together to create a healthy growing environment for each other, provided that the system is properly balanced.
Although the production of fish and vegetables is the most visible output of aquaponics system, it is essential to understand that aquaponics is the management of a complete ecosystem that includes three major groups of organisms: fish, plants and bacteria.
Water Quality for Aquaponics System
Temperature (°C) : 18 – 30 °C
pH: 6 – 7
Ammonia (NH3-): < 1 ppm (0.25 ppm)
Nitrite (NH2-): < 1 ppm (0.25 ppm)
Nitrate (NO3-): 5 – 150 ppm
Potassium (K2O): 50 – 100 ppm
Calcium (CaO): 80 – 150 ppm
Iron (Fe): 2 – 3 ppm
Dissolve Oxygen (DO) : 5 – 8 ppm
GH: 60 – 140 ppm
KH: 60 – 140 ppm
EC: < 1.50 ms/cm
How often to check
1. During initial setup
Ammonia, Nitrite, Nitrate, pH should be monitored daily
2. After for a while when aquaponics system stable
• Ammonia, Nitrite, Nitrate, EC 2 times per week
• pH daily
• Potassium, Calcium, Iron, GH and KH weekly
Aquaponics Plant Selection
Vegetables vary regarding their overall nutrient demand. There are two general categories of aquaponics plants based on this demand. Low-nutrient demand plants include the leafy greens and herbs, such as lettuce, basil, mint, parsley, coriander and pak choi.
At the other end of the spectrum are plants with high-nutrient demand, sometimes referred to as nutrient hungry. These include the botanical fruits, such as tomatoes, eggplants, cucumbers, strawberries and peppers. Other plants with medium nutrient demands are: cabbages, broccoli and others.
If aquaponics water nutrients not enough supply to plants, you will need to foliar spray to supply the necessary nutrients to plants.
What is General Hardness (GH)?
GH is a measurement of the minerals, such as calcium and magnesium ions, in the tank. These enter the tank via tap water, and they remain when water evaporates from the tank.
What is Carbonate Hardness (KH)?
KH is a measurement of the total carbonate in the tank. Carbonate is found in materials such as limestone or seashells, as well as in baking soda (sodium bicarbonate). Carbonate stabilizes the pH of an aquarium, and also serves as a source of energy when oxidizing the waste ammonia in the tank.
Essential nutrient to all plants including N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, Mo, Si, Na, Cl, Ti. Irrespective of whether the fertilizer source is organic, mineral or chemical, plant’s root system can only take in nutrient in ionic form.
Nutrition greatly affects a plant’s susceptibility to disease. It also affects a plant’s ability to respond against disease using different mechanisms, including antixenosis (processes to deter colonization by herbivores) or antibiosis (processes to kill or reduce herbivores after landing or during eating). A correct balance of nutrients not only provides optimal growth but also makes plants less susceptible to diseases. Below table outlines how some nutrients can play a major role in disease occurrence.
Effect of nutrients on fungal disease prevention
1. Nitrogen (N): Over fertilization makes more succulent tissues that are more prone to fungal attack. Nitrogen starvation makes stunted plants more prone to attacks from opportunistic micro-organisms.
2. Phosphorus (P2O5): Improves nutrient balances and accelerates the maturity of the plants.
3. Potassium (K2O): Accelerates wound healing and reduces the effect of frost damage. Delays maturity and senescence of plants.
4. Calcium (CaO): Reduces the severity of some root and stem fungal diseases. Affects the cell wall composition in plants that resists fungal penetration.
5. Silicon (Si): Helps plants to produce specific defense reactions, including the release of phenolic compounds against pathogens.
What is Electrical Conductivity (EC)?
Here it is important to consider an additional water quality parameter: salinity.
Salinity indicates the concentration of salts in water, as well as plant nutrients, which are in fact salts. Salinity levels will have a large bearing when deciding which water to use because high salinity can negatively affect vegetable production, especially if it is of sodium chloride origin, as sodium is toxic for plants. Water salinity can be measured with an electrical conductivity (EC) meter or a total dissolved solids (TDS) meter.
EC (mS/cm) = TDS (ppm) / 500
EC (mS/cm) = EC (µm/cm) / 1000