From our experience with aquaponics, most all systems available do not fully address all the basic necessities of an aquaponics system. Dr. James Rakocy (considered the "Father of Aquaponics") with the University of Virgin Islands, has spelled it out the best, in my opinion. Following are his 10 most important aspects of a well-designed, well-working Aquaponics system.
Use A Feeding Rate Ratio For Design Calculations
Keep Feed Input Relatively Constant
Supplement with Calcium, Potassium, and Iron
Ensure Good Aeration
Be Careful with Aggregates
Use Biological Control
Ensure Adequate Biofiltration
Although some of these aspects relate to the maintenance of a system, others do address the design aspects of a system.
Ensure Proper Aeration
There are negative effects of both under-aeration and over-aeration. Although most information on the internet will promote high aeration, there is a condition which Tilapia can develop from over-aeration, called "Popeye". Heavy bubbling from deep in a tank, creates a pressure within the water, which is greater than the surrounding air pressure. This will cause the eyes to bulge outward. If not caught immediately, this condition may result in permanent blindness.
"Approximately 25% of the feed given to fish is excreted as solid waste, based on dry weight. However the wet weight of the solid waste is considerably greater. It is advisable to remove this solid waste from the flow stream through filtering or settling before it enters the hydroponic component. If solids are not removed, they will adhere to plant roots, decrease oxygen levels as they decay, and affect the uptake of water and nutrients. Excess solids will also have an adverse effect on nitrifying bacteria. Moreover, as solids decompose, oxygen is consumed and ammonia is produced."
Be Careful With Aggregates
"Aggregates such as pea gravel, sand and perlite are excellent media for growing plants in hydroponic systems. However, the solid organic matter generated in aquaponic systems can clog aggregate media and channelize water flow. Water will not flow through the clogged areas, which will become anaerobic (without oxygen) as the organic matter decomposes, thereby killing the plant roots."
Ensure Adequate Biofiltration
"After removing solids, the next stage in the treatment process of a recirculating system is the biofiltration or the oxidation of ammonia to nitrate by nitrifying bacteria". Biofilters are essential for the health of the fish and plants.
"Use oversized pipes to reduce the effects of bio-fouling. High levels of dissolved organic matter in aquaponics systems promote the growth of filamentous bacteria inside pipes and restrict flow. Pipes that are located downstream from the solids removal component and biofilter are less likely to clog because the dissolved organic matter has been removed or reduced through biological activity in the biofilter."
A lack of attention to any of the above design aspects, can make your system look like these