| • Science | • People | • Locations | • Timeline |
| Contents | ||
One of the largest problems with aquaculture is that it can use a million gallons of water per acre (about 1 m³ of water per m²) each year. Recycling solves that problem.
The largest-scale pure fish farms use a system derived (admittedly much refined) from the New Alchemist s in the 1970s. Basically, large plastic fish tanks are placed in a greenhouse. A hydroponic bed is placed near, above or between them. When tilapia are raised in the tanks, they are able to eat algae, which naturally grows in the tanks when the tanks are properly fertilized.
The tank water is slowly circulated to the hydroponic beds where the Tilapia waste feeds a commercial crop such as parsley. Carefully cultured microorganizms in the hydroponic bed convert ammonia to nitrates, and the plants are fertilized by the nitrates and phosphates. Other wastes are strained out by the hydroponic media, which doubles as an aerated pebble-bed filter.
This system, properly tuned, produces more edible protein per unit area than any other. A wide variety of plants can grow well in the hydroponic beds. Most growers concentrate on herbs, which command premium prices in small quantities all year long. The most common customers are restaurant wholesalers.
Since the system lives in a greenhouseSaint Paul, Minnesota. A greenhouse (or glasshouse is a building where plants are cultivated. A greenhouse is built of glass or plastic; it heats up because the sun's incoming electromagnetic radiation (particularly infrared light) warms plants, soil, and, it adapts to almost all temperate climates, and may also adapt to tropical climates.
The main environmental impact is discharge of water that must be salted to maintain the fishes' electrolyteAn electrolyte is a substance which dissociates free ions when dissolved (or molten), to produce an electrically conductive medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutes . They are sometimes refer balance. Current growers use a variety of proprietary tricks to keep fish healthy, reducing their expenses for saltFor other meanings of the word salt see salt (disambiguation In chemistry, a salt is a composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. They are typically the product of a chemi and waste water discharge permits. Some veterinary authorities speculate that ultraviolet ozone disinfectant systems (widely used for ornamental fish ) may play a prominent part in keeping the Tilapia healthy with recirculated water.
A number of large, well-capitlized ventures in this area have failed. Managing both the biology and markets is complicated.
Reference: "Freshwater Aquaculture: A Handbook for Small Scale Fish Culture in North America" by William McLarney
These use irrigationSahara Irrigation (in agriculture) is the replacement or supplementation of rainfall with water from another source in order to grow crops. In contrast, agriculture that relies only on direct rainfall is sometimes referred to as dryland farming. How it wo ditches or farm ponds to raise fish. The basic requirement is to have a ditch or pond that retains water, possibly with an above-ground irrigation system (many irrigation systems use buried pipes with headers). This is a low-investment way to produce fish from an existing structure. Often the fish sell for premium prices since they are fresh, and produced inland. If the ponds raise sport species, they can be advertised as "fishing ponds," and access can be sold directly to fishermen.
Using this method, one can store one's water allotment in ponds or ditches, usually lined with bentonite clay. In small systems the fish are often fed commercial fish food, and their waste products can help fertilize the fields. In larger ponds, the pond grows water plants and algae as fish food. Some of the most successful ponds grow introduced strains of plants, as well as introduced strains of fish.
Control of water quality is crucial. Fertilizing, clarifying and pHAlternate uses: see Ph pH (potential (of) hydrogen) is a measure of the concentration of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S. Sorensen in 1909. The p stands for the German potenz mean control of the water can increase yieldYield may mean: In economics, yield is a measure of the amount of income an investment generates over time (related to return on investment). For example, farmers talk of the yield per unit area of land. In finance, the yield on a security is the return fs substantially, as long as eutrophicationCaspian Sea as imaged from orbit. Eutrophication is the enrichment of an aquatic system by addition of nutrients. It is typically caused by leached phosphorus or nitrogen containing compounds into lakes, rivers, bays, or other semi-enclosed waters (even s is prevented and oxygen levels stay high. Salting the water is not recommended because it can salinize the fields. Yields can be low if the fish grow ill from electrolyte stress.