Introduction to Fish Farming In Tanks
Fish farming involves raising fish commercially in tanks. Farmed fish for subsistence food has become popular in recent years as more people seek to provide healthy sources of farmed fish for their families. Fish farming can be done on a small scale in ponds, pools, or tanks.
Tanks allow the fish culturist to easily manage stocks and to exert a high degree of environmental control over parameters like water temperature, Dissolved Oxygen (DO), pH, and waste that can be adjusted for maximum fish production. If raising fish in tanks, feeding and harvesting operations require less time and labor compared to ponds. Small tank volumes make it practical and economical to treat some diseases with therapeutic chemicals dissolved in the culture water. Intensive tank culture can produce high yields on small parcels of land.
A Step by Step Guide to Fish Farming In Tanks
Rearing tank means a tank where the fry are reared into fingerlings (to attain a size of 10 – 15 cm) and the culture duration is 2 – 3 months. The size of the tank varies from 0.05 – 0.1 hectare with a water depth of about 1.5 – 2.0 m.
The recommended characteristics for fish raising in tanks are as follows;
- The interior surface in tanks should be smooth to prevent abrasion.
- The surfaces should be nontoxic.
- The tanks must be durable and portable, have a long life, ease of cleaning, easy to sterilize.
- It must be non-corrosive and affordable.
Different Varieties of Tanks Used for Fish Farming
Tanks come in a different variety of shapes, but the most common forms are circular and rectangular. Variations of circular tanks are silos, which are deep and octagonal tanks.
Shapes of tanks are mainly circular, rectangular, square, and oval tanks.
Circular tanks are commonly used for nursery and grow out purposes also used. It has a better hydraulic characteristic. The self-cleaning action and oxygen distribution of circular tanks hold specific benefits. The circulation of water will cause a better mixing of oxygen, food distribution, and higher stock densities.
Square and Rectangular tanks have efficient use of space. It contributes to savings on construction costs. The main disadvantage of square and rectangular tanks is that wastes tend to collect in the corners. The corners of square or rectangular tanks are often rounded to improve the hydraulics and flow patterns.
Oval tanks are an effort to combine the advantages of circular tanks and rectangular tanks. It has efficient water use and self-cleaning action of the circular tank and the space efficiency of rectangular tanks. It is found in intensive indoor and outdoor systems, where aeration technology is applied.
Circular tanks are popular because they tend to be self-cleaning. Rectangular tanks are very easy to construct but often have poor flow characteristics. Incoming water can flow directly to the drain, short-circuiting the tank, while other areas of the tank become stagnant, which allows waste to accumulate and lowers oxygen levels. For these reasons, circular tanks provide better conditions than rectangular tanks for tilapia fish culture. Though circular culture tanks can be as large as 100 feet in diameter, common sizes range from 12 to 30 feet in diameter and 4 to 5 feet in depth. Rectangular tanks are mainly variable in dimensions and size, but raceways have specific dimension requirements for proper operation.
Why is pH Level Important in Tanks for Fish Farming?
Different species of fish like different water conditions and will live longer if it is correct, so you need to take some care and attention. Absorb which fish can exist in the tank and adjust your maintenance schedule to ensure that the water is in the prime condition for them. Failure to do this can result in high levels of fish fatality.
The pH level of the tank should vary depending on fish species selection. To discover what condition your water is in, you will have to complete regular pH level testing.
Below are the appropriate pH levels for each type of tank;
- Freshwater tanks – pH level of between 5.5 and 7.5 depending on fish species
- Tropical water tanks – pH level of 6.0 to 7.0
- Marine water tanks – pH level of 7.6 to 8.4
- Reef tanks – pH level of 8.0 to 8.4
Materials Used for Tanks Construction for Fish Farming
Materials used for tanks construction are;
1) Wooden tanks
- They are cheap
- Light in weight
- All surfaces must be painted to protect the wood.
- Do not use paints that have lead as this leach into the water.
- The interior of the tank must be covered with non-toxic materials such as epoxy or fiberglass resin paint. They cure in 2 days, forming a hard and smooth surface.
- Waterproof liners may be used in wooden tanks
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2) Concrete Tanks
- Concrete material is used for large tanks.
- Tanks can also be made from gunite which is strong, compact, but is more expensive than liners
3) Plastic Tanks
- Plastic includes polypropylene, polybutylene, polyethylene, polyvinyl chloride (PVC), acrylics, and vinyl. And, each one has its own bad and good qualities.
- Advantage of plastic tanks include; it is lightweight, portable, repairs are easier, can be made in various shapes and sizes, most are non-toxic.
Fiberglass is mostly chosen for tank construction because of its lightweight, strong, durable, inert, and can withstand the effects of UV rays.
Tank Design Considerations for Farming Fish in Tanks
Properly designed tanks with proper inlet piping and a central drain take advantage of gravitational and centrifugal forces to keep themselves clean. Then, 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. A properly designed tank improves space utilization inside the tank, and this allows the production of more pounds of fish per unit of water flow. The water flow direction can be reversed periodically, helping to even out fish growth by rearranging their feeding order. Then, by avoiding the need to clean the tank floor of sediments both fish stress and labor costs are reduced. The solids are easy to separate with an efficient swirl separator or a high-efficiency micro screen filter. Also, an inspection of the solids removed from the effluent stream allows for more precise feeding control.
An oxygenated round tank system can grow more pounds of fish with less feed than a comparable area of ponds. Utilizing prefabricated glass-coated steel tank kits can reduce the cost of installation. The smooth tank surface mainly helps to eliminate disease vectors and skin abrasions, while providing a long-lasting, economical tank. Selection of a tank diameter: depth ratio is mainly influenced by some factors such as the cost of floor space, and fish stocking density, fish species, and fish feeding levels.
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Circular Tanks for Raising Fish
Tanks are designed with some considerations such as production cost, space utilization, water quality, fish feed, and fish management.
Circular tanks make good culture vessels for the below reasons;
- Simple to maintain
- Provide uniform water quality
- Circular tanks improve the uniformity of the cultural environment
- Circular tanks allow a wide range of rotational velocities to optimize fish health
The fish farming in large circular tanks produced large cost savings in comparison to raising the same quantity of fish in more but smaller tanks. Larger circular culture tanks offer many benefits for food fish production.
The ability to self-clean is the main advantage of circular tanks. To establish this ability, the water column should be in constant rotation within the tank. To make the tank self-cleaning, the rotational velocity in the tank must be uniform from the tank wall to the center and from the surface to the bottom. Though, it should not be faster than that required to exercise the fish. Circular tanks maintained good water quality throughout the tank by optimizing the water inlet structure. By selecting a water exchange rate so that the limiting water quality parameter does not decrease fish production when the system reaches carrying capacity.
The water inlet and outlet structures reduce the labor requirement for fish handling and get uniform water quality and solids removal within the circular tank. There is nothing more irritating than pipes and devices that are in the way when it is time to harvest fish in a tank. Such obstructions may decrease the effectiveness of the self-cleaning attributes of round tank culture. Though, inlet structures can be installed for ease of removal during harvesting when supplemental aeration devices are operated as well.
Filter System for Fish Farming in Tanks
The filter system consists of a 25-gallon stock tank, a 5-gallon bucket, some lava rock and gravel, and a 750 gallon/hour ornamental pond pump. Also, 12-volt pumps are available and are a good idea in the event of a power failure. The filter is constructed by drilling a bunch of holes in the side of the bucket, up to 6 inches from the bottom. This bucket is located in the middle of the stock tank, weighted down with a brick. The lava rock and gravel are added to the stock tank within 3 or 4 inches of the top of the tank.
Then, the water pump is placed in the center of the bucket. The lava rock and gravel provide a substrate for the bacteria that digest fish waste. The placement of the holes in the bucket ensures that all water will be drawn through the gravel. The pump returns water to the tank, and water spills into the filter tank from an overflow pipe in the pool.
Tilapia Fish Farming in Tanks
Raising tilapia in tanks is a good alternative to pond or cage culture if sufficient water or land is not available and the economics are favorable. Then, this is accomplished by aeration and continuous water exchange to renew dissolved oxygen (DO) supplies and remove wastes. It can eat algae, which naturally grow in the tanks when the tanks are properly fertilized. If you want to grow Tilapia in colder climes, tank culture is the best bet. Tilapia is quite hardy and can tolerate a wider range of water conditions than many species. Tilapia raising in tanks is quite common in regions where suitable land for tilapia cultivation is scarce or there is a shortage of inexpensive water. Compared to pond farming of tilapia the stocking density is usually high in tanks.
The advantages and disadvantages of tank culture of tilapia compared to pond raising;
Advantages of Raising Tilapia in Tanks;
- It is easier and less labor-intensive to harvest tilapia from tanks instead of ponds.
- The stocking density utilized in tanks disrupts the normal breeding behavior of tilapia, so you can raise tilapia without having to worry about uncontrolled spawning. The fish will not spend energy on reproducing instead of growing, and they will not be forced to compete with their offspring from space and food.
- If raising Tilapia in tanks, the environment inside a tank is easier to control than that of an outdoor pond. This applies to a long row of environmental factors like water temperature, oxygen content, and pH-value.
Disadvantages of Raising Tilapia in Tanks;
- Inside a tank, tilapias do not have access to any naturally occurring sources of food and you will have to feed them a lot of food and make sure their diet is complete. Fish feeding too little or using low-quality food can decrease growth rates, harm the immune system, and make the fish less nutritious.
- The high stocking density utilized in tanks makes the Tilapia more susceptible to poor health. You can counteract some of the risks by keeping the water quality pristine and feed your fish a suitable and nutrient-rich diet.
- Tilapia fish have limited access to natural foods in tanks; they must be fed a complete diet containing vitamins and minerals. The cost of water pumping and aeration increases production costs.
Best Breeds for Fish Farming in Tanks
Blue Tilapia – Blue Tilapia are best for raising fish in tanks because they are the coldest tolerant. If you don’t wish to buy fresh stock for each grows outrun, you can start a breeding colony in a smaller tank, or even in large tanks. Stocking densities must be modest to avoid a great deal of water quality and feed management. Assuming a target weight of about 2-2.5 lbs/fish, you should keep your density down to one fish every 5 to 10 gallons of tank volume.
Blue Nile Tilapia – It is also called Rocky Mountain White tilapia, is one of the most popular varieties for small scale aquaculture systems. They are fast-growing, disease-resistant, tolerant of poor water conditions, and quite beautiful. The optimal water temperature will be 23 to 29°C.
Salmon – Salmon have similar requirements as trout but are more sensitive to poor water quality. An added complexity is that they are raised from eggs, which requires a bit more technical knowledge to pull off. The optimal water temperature level will be 7 to 12°C.
Trout – Trout grow slowly but their excellent flavor may be worth the time investment needed to learn how to raise them successfully. The optimal water temperature will be 10 to 15°C.
Catfish – Catfish raising in tanks is not only easy but also great for you that do not have a large enough land to make large-scale catfish farming. The fishes adapt to a wide range of water conditions. The optimal water temperature will be 23 to 29°C.
Perch – There is a variety of perch suitable for small scale tanks, though yellow perch, a native of the Great Lakes, is the most common species. These fish species produce faster than most other perch, but still not as fast as tilapia.
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