There has been a significant shift towards round tanks for fish rearing. Properly designed round tanks with a central drain, moderately sloped floor and proper inlet piping take advantage of gravitational and centrifugal forces to keep themselves clean. The water moving in a circular flow will carry the solids to the central drain, from where they can be piped away for separation and re-use or disposal. With a properly designed inlet system, the oxygen rich water will provide just the right current for good muscle tone while distributing new water evenly throughout the tank.
This design improves space utilization inside the tank, and allows the production of more pounds of fish per unit of water flow. The water flow direction can also be reversed periodically, helping to even out growth of the fish class by rearranging their feeding order. By avoiding the need to clean the tank floor of sediments both fish stress and labor costs are reduced. Once the fish feces and uneaten feed are in a drain pipeline, it is relatively easy to separate these solids with either an efficient swirl separator (comparable in efficiency to a settling pond only using much less space) or a high efficiency micro screen filter.
From there the solids can be pumped to storage for seasonal reuse as a soil additive, a great fertilizer with humus value. Inspection of the solids removed from the effluent stream also allows for more precise feeding control. An oxygenated round tank aquaculture system can grow more pounds of fish with less feed, less water and less stress than a comparable area of raceways or ponds. Utilizing prefabricated glass coated steel tank kits can significantly reduce the cost of installation. The smooth tank surface further helps to eliminate disease vectors and skin abrasions, while providing a long lasting, economical tank.