Bacteria and worms play a significant role in your Aquaponics system. They are responsible in converting ammonia, liquid waste, and solid waste from the fish to plant food. Without them, your Aquaponics will surely fail!
I. Nitrifying Bacteria
While there are literally hundreds of types of bacteria that will home into your Aquaponics system , there are only two that we primarily focus on because they do the job of converting the toxic ammonia from the fish into benign nitrate: Nitrosomonas and Nitrobacter. They are of a family of autotrophic bacteria called “nitrifying bacteria”. When your Aquaponics system is constructed and ready to be used for the first time there will be virtually no beneficial bacteria present, colonies of Nitrosomanas and Nitrobacter must be established before the system will work correctly. The process of establishing the bacteria colonies in your Aquaponics system is referred to as cycling your system. The primary purpose of cycling process during start up of your Aquaponics is to attract these two naturally occurring friends to your systems.
The amount of time that it takes for your bacteria colonies to become established depends on many variable factors such as water temperature, ambient temperature, the depth of the grow bed and many other things besides. In a warm temperate or tropical climate you may have colonies starting to establish themselves in as little as two to three weeks. It may take substantially longer if conditions are less than optimal.
Bacteria are so small its really difficult to tell if your system has cycled successfully but there is one sure way to tell in the form of an aquarium water test kit. Aquarium water test kits allow you to measure the amount of ammonia, nitrite and nitrate in parts per million and also the pH level of your water. They can be purchased at reasonable cost from aquariums and pet shops and most kits permit hundreds of tests to be performed. I recommend testing every day once you have added your source of ammonia. What you should see is the ammonia levels slowly rise to about 5ppm or so and then drop to zero as the Nitrosomanas bacteria become established. Nitrite levels will then start to rise to about 5ppm and then once again drop to zero as the Nitrobacter also become established and start producing nitrates.
When you can see the presence of nitrates it is time to add your fish to the tank and plant your vegetables in the grow bed.
Facts on Nitrifying Bacteria
Some facts that might be interesting about nitrifying bacteria are:
- Nitrifying bacteria are classified as obligate chemolithotrophs. This simply means that they must use inorganic salts as an energy source and generally cannot utilize organic materials. They must oxidize ammonia and nitrites for their energy needs and fix inorganic carbon dioxide (CO2) to fulfill their carbon requirements.
- Nitrifying bacteria are largely non-motile and must colonize a surface (gravel, hydroton, sand, synthetic biomedia, etc.) for optimum growth. They secrete a sticky slime matrix which they use to attach themselves.
- Nitrifying bacteria have long generation times due to the low energy yield from their oxidation reactions. Since little energy is produced from these reactions they have evolved to become extremely efficient at converting ammonia and nitrite. Scientific studies have shown that Nitrosomonas bacterium are so efficient that a single cell can convert ammonia at a rate that would require up to one million heterotrophs to accomplish. Most of their energy production (80%) is devoted to fixing CO2 via the Calvin cycle and little energy remains for growth and reproduction. As a consequence, they have a very slow reproductive rate.
- Nitrifying bacteria reproduce by binary division. Under optimal conditions, Nitrosomonas may double every 7 hours and Nitrobacter every 13 hours. More realistically, they will double every 15-20 hours. This is an extremely long time considering that heterotrophic bacteria can double in as short a time as 20 minutes. In the time that it takes a single Nitrosomonas cell to double in population, a single E. Coli bacterium would have produced a population exceeding 35 trillion cells.
- Nitrifying bacteria is sensitive to pH, dissolved oxygen levels, salt, temperature, and inhibitory chemicals.
Factors that affect the growth of Nitrifying Bacteria
The temperature for optimum growth of nitrifying bacteria is between 77-86° F (25-30° C).
Growth rate is decreased by 50% at 64° F (18° C).
Growth rate is decreased by 75% at 46-50° F.
No activity will occur at 39° F (4° C)
Nitrifying bacteria will die at 32° F (0° C).
Nitrifying bacteria will die at 120° F (49° C)
Nitrobacter is less tolerant of low temperatures than Nitrosomonas. In cold water systems, care must be taken to monitor the accumulation of nitrites.
The optimum pH range for Nitrosomonas is between 7.8-8.0.
The optimum pH range for Nitrobacter is between 7.3-7.5
Nitrobacter will grow more slowly at the high pH levels. Initial high nitrite concentrations may exist. At pH levels below 7.0, Nitrosomonas will grow more slowly and increases in ammonia may become evident. Nitrosomonas growth is inhibited at a pH of 6.5.
All nitrification is inhibited if the pH drops to 6.0 or less. Care must be taken to monitor ammonia if the pH begins to drop close to 6.5. At this pH almost all of the ammonia present in the water will be in the mildly toxic, ionized NH3+ state.
- Dissolved Oxygen (DO).
Maximum nitrification rates will exist if dissolved oxygen (DO) levels exceed 80% saturation. Nitrification will not occur if DO concentrations drop to 2.0 mg/l (ppm) or less. Nitrobacter is more strongly affected by low DO than Nitrosomonas.
Nitrifying bacteria are photosensitive, especially to blue and ultraviolet light. After they have colonized a surface this light poses no problem. During the first 3 or 4 days many of the cells may be suspended in the water column.
Chlorine is not desirable in Aquaponics systems for two reasons, firstly it damages the gills of your fish and kills them and secondly it kills your beneficial bacteria too. Chlorine must be removed from your water before adding it to the Aquaponics system. Chlorine can be added to drinking water in one of two ways.
If it is added as chlorine gas then it will dissipate fairly quickly if you put your water into a bucket or container and allow it to stand for a day or two. If the chlorine is added as chloramine or you would like to use your water immediately there are water conditioners you can buy from pet shops and aquariums that will chemically remove the chlorine for you. If you choose to use a water conditioner or chlorine neutralizer ensure that it is suitable for use with fish intended for human consumption.
II. Red Worm
Worms are an incredible asset to any media based Aquaponics system.They break down the solid waste from the fish, and excess roots and other biodegradable materials and make them more bio-available to the plants through their waste called worm casting or vermicompost. Worms are one of the nature’s great garbage disposal.
Researcher found out that worm casting soaked in Oxygenated water(“tea”) provides the following benefits in increasing seed germination and plant growth. Their studies have concluded that vermicompost and the corresponding “tea” are tremendously beneficial because they:
- Suppress plant disease including Pythium, Rhizoctonia, Plectosporium, and Verticillium.
- Suppress plant parasitic nematode.
- Suppress plant insect pests, including tomato hornworms, mealy bugs, spider mites and aphids.
They are valuable waste conversion machine, freeing up precious nutrients for your plants. They mitigate the need for frequently cleaning your beds. They help manage plant disease and harmful insects and nematodes, and they work to help render pathogens harmless. They are indeed Aquaponics secret ingredient!