Aquaponics, sustainable solution or suspect system?

The essential concept of aquaponics is simple in the extreme. Waste food is fed to fish, which on turn convert this into animal protein. The waste products from the fish (faeces and soluble minerals) are in turn converted by bacteria in the system into soluble mineral ions, which are absorbed by the plant roots. The “cleaned” water is then returned to the fish tank. Thus a waste product is converted into two valuable products (fish protein and a high value horticultural crop) with the minimum use of water, and minimum use of expensive nutrients (as are required in hydroponic systems). The down sides are that high quality fish feed is not cheap, and is likely to get even more expensive in the future as wild fish stocks decline; The optimum pH for fish tend to be above 7.0, whereas for most crop plants it tends to be about 6.0; the bulk of the income is derived from the horticultural operation, which therefore has to compete with conventional hydroponic producers. It takes someone with very special skills to manage both a fish and a horticultural operation effectively and it takes time for the operation to come on line. The potential for using media based hydroponic systems in aquaponics, and the production of fruit vegetables using aquaponics is difficult. It is extremely difficult to obtain organic certification for the horticultural operation (except in USA). On the other hand there are several advantages of the system: no expensive fertilizer requirements; the ecological balance appears to reduce pathogen problems, it is considered to be an environmentally friendly system, with no waste products needed to be disposed of from either the fish or plant side. Other factors (such as the ω3 content of the fish, and the difficulties of organic certification) will also be considered.