Homemade or sold by a commercial builder, aquaculture fish tanks come in a variety of sizes and shapes from just a few meters in diameter and volume to the size of a pond. In terms of shape, round tanks, raceways, and D-ended tanks of one form or another are the basic types used in onshore recirculating aquaculture systems (RAS) today. Alhough a range of materials have been used to build aquaculture tanks, fiberglass, steel, and concrete are probably the most commonly used commercially. In choosing a suitable aquaculture tank or tanks, a person must strike the right balance between what is required to raise a given quantity of a species in an environmentally sound manner while operating within budget constraints.
Important factors to consider when deciding which type of aquaculture tank to buy or build include whether it will hold freshwater or saltwater, the type and quantity of fish to be raised and their development requirements, and the amount of space available. Other important considerations when choosing the type of aquaculture tank are the ambient weather and climate and the availability of critical inputs such as water and power. When it comes to materials, it's critical that tanks are watertight, non-corrosive, non-toxic, non-abrasive and can retain their shape under pressure.
Round aquaculture tanks are often found in fish hatcheries. Their shape, generally with sloping sides, along with the fact that the outlet is located at the bottom center, means that the comparatively high level of solid waste hatcheries produce will wind up at the outlet due to water circulation. This makes for simple and efficient waste removal before the waste products can break down. Round tanks make it easier to maintain a constant rate of circulation, which many species prefer. They also assure a good mixing of water, which makes for easier oxygenation, and minimize the contact by the fish with tank sides and bottom.
Typically built with a width to depth ration of 2:1 or 4:1, conventional raceway tanks are straight-sided artificial channels in which the fish are held. Straight raceways have a high rate of water turnover. High fish stocking density and high flow rates are required for a conventional raceway to be self-cleaning. Maintaining adequate water mixing and oxygenation are also more problematic as compared to round tanks; modifications such as sloping bottoms and aeration have been tried and shown to be effective, however. On the other hand, straight raceways are relatively easy to build and expand, and they make it relatively easy to separate and remove fish, as screens can be placed and removed with ease.
So-called D-ended aquaculture tanks of various shapes and sizes are another standard configuration. "D-ended" refers to a central dividing panel. D-ended aquaculture tanks may be round, oval, octagonal, or straight channels, as in a conventional raceway. Variations of these standard configurations, such as "silos" and cross-flow raceways, are also in use.
