Introduction
Aquaponics is the integration of aquaculture (fish farming) and
hydroponics (growing plants without soil). In aquaponic system the
fish consume food and excrete waste primarily in the form of ammonia.
Bacteria convert the ammonia to nitrite and then to nitrate [1-14].
Aquaponics has several advantages over other recirculating
aquaculture systems and hydroponic systems that use inorganic
nutrient solutions. The hydroponic component serves as a biofilter,
and therefore a separate biofilter is not needed as in other recirculating
systems. Aquaponic systems have the only biofilter that generates
income, which is obtained from the sale of hydroponic produce such as
vegetables, herbs and flowers [15].
Small proportion of ammonia is toxic to fish, when as nitrate is not
toxic to fish. If nitrate increased over a specific limit it will be toxic to
fish eaters (human being) and cause nitrate pollution and the eaters
will suffer from methamoglobnia disease. The blood of the affected
people became brown and will not be able to carry oxygen to the rest
of human organs [16]. To avoid this problem in aquaculture, part of
water should be discharged daily and add fresh water instead. Another
solution to this problem is establishing hydroponic system attached to
the aquaculture and cultivates plants in the hydroponics in order to
save discharged-water and gets use of existing nitrate.
Benefits of aquaponics are conservation of water resources and plant
nutrients, intensive production of fish protein and reduced operating
costs relative to either system in isolation. Water consumption in
integrated systems including tilapia production is less than 1% of the
required in pond culture to produce equivalent yields [4].
Lettuce is one of the best crops for aquaponic systems because it
can be produced in a short period and, as a consequence, pest pressure
is relatively low. Unlike tomato and cucumber, a high proportion of the
harvested biomass is edible. With lettuce, income per unit area per unit
time is very high. Other fast growing and high income generating crops
are herbs such as basil and chive, which are being grown commercially
in aquaponic systems [15].