A Word About Stocking Densities
Aquatic life stocking densities is a function of the amount of feed processed y your aquatic life and the amount of resultant waste that can be filtered by the system. “Naturally balanced” systems relying on bacteria, worms, and aquatic life as the filtration system will support far less fish per tank than will systems incorporating more sophisticated filtration systems. Systems using only grow media, bacteria, and worms for mechanical and biological filtration support smaller densities of aquatic life but also require less labor and equipment than do systems incorporating additional filtration systems. Higher densities of aquatic life can be achieved, but do require greater effort and expense.
Experts and experienced aquaponists report that a “naturally balanced” system typically supports 1 lb of grown out fish for 5 to 10 gallons of water. In this case, a tank of 100 gallons would support 10 to 20 table sized fish. Introducing additional waste removal techniques with additional components such as charcoal filtrations, UV systems, clarifying, mineralizing, and degassing tanks, may support up to 1 lb of fish per 1.5 to 3 gallons of tank water. This latter goal also requires more intense management, greater labor, and expense in both setup and maintenance. Disposal of waste may also be problematic from a regulatory perspective. These considerations are very often the driving factors moving home and hobby aquaponists to “naturally balanced” media base growing systems.
A Word About Grow Bed Densities
Grow bed densities are basically a function how much waste is available for conversion to plant nutrients, how well the grow bed bio-filter can convert the waste to nutrients, and sunlight and water availability. The more nutrients available, the greater the ability to increase plant density. Remember that plants require sufficient sunlight and water as well. Even at traditional spacing, aquaponic systems can readily produce 5 to 8 times the amount of plant harvest as an equivelant traditional gardening (don’t forget the significant water usage reduction as well!).
The Relationship between Stocking Densities and Grow Bed Densities
High densities of both stock and grow bed densities can be achieved by introducing additional resources together with nutrition, areation, and water quality improvement techniques. In the absence of such techniques, in a media based system, a good ratio to work with is approximately 1 cubic foot (7.5 gallons) of grow bed per 1 pound of grown out fish. If one adopts the 5-10 gallons of aquatic life tank volume per 1 pound of fish, then roughly 1 cubic ft of aquatic life tank will support 1 cubic ft of grow bed. This suggests a 1:1 ratio of volumes between the aquatic life tank and the grow bed. Though many home-based aquaponists adhere to this ratio, with a bit of patience and effort, 1:2 ratios and greater may be achieved.
Choosing the System for You
Your system design will be a function your goals, your resources, and abilities. Remember. Aquaponic can be extremely enjoyable and rewarding. It is, however, it is an investment in an ongoing effort. Consider your initial investment, as well as your ongoing investments.
If you are new to gardening, stock management, or aquaponics, smaller may be the better way to start.
Though aquaponics is not difficult to master, it is far better to minimize risk and effort until you are certain your interest is more than passing. Expanding your system, or developing larger systems is easy and straight forward.
Carefully consider your investments and commitment as well as the characteristics and costs associated with each design type before you begin.