Tilapia is the most common fish used for aquaponics as well as aquaculture. It grows efficiently and is extremely adaptive to different water conditions, although how big do tilapia get? Furthermore, they have a high survivability rate even in stressful environments. It is a great fish to use for aquaponics, both for beginners and experienced growers. Raising tilapia in tanks for aquaculture has been well studied over the years as it is a common source of protein in most countries. Although, the growth rate has always been a concern of aquaculturists around the world and it varies per region and per practice.
To understand tilapia and its growth rate in aquaponics, we’ll need to first understand parameters that affect the growth of tilapia in aquaculture tanks
What Affects Tilapia Growth Rate In Tanks For Aquaponics?
As the growth of tilapia in fish tanks has been widely studied, practices, ideal parameters, and responses to environmental changes have been recorded in detail. However, there is no standard yield or growth for tilapia as aquaculture operations depend widely on environmental conditions and practices. Tilapia growth cycles have different stages and most practitioners of aquaculture purchase fingerlings and focus on their grow-out operations which take 5 to 6 months per cycle.
We will be discussing parameters that directly affect the size of the tilapia and the rate of growth more than parameters that affect survivability. With this in mind, we will be assuming that parameters like nitrite, salinity, chlorine, dissolved oxygen, and diseases are kept within allowable limits that do not cause stress for the fish.
Higher Fish Stocking Density Lowers Growth Rate and Maximum Growth Of Individual Fish
High fish stocking density is a common practice for aquaculturists to maximize yields. Although this is attractive considering more fish equals more yield, it does not translate to efficient growth rates. High fish stocking density works well for locations with lower market sizes. This is because of less room to grow for the fish in the tank. According to a research on growth rates of different fish stocking densities done in fish ponds, the lowest fish stocking density recorded the highest average weights per individual fish.
It is suggested by the Southern Regional Aquaculture Center (SRAC) to compute for the desired stocking density during full growth of the tilapia when designing your tank’s fish stocking density.
Temperature is another crucial parameter that affects the growth rate of aquaculture in general. According to James Rakocy from SRAC, the preferred temperature for tank culture of tilapia ranges from 82° to 86°F. The cost of growing will be lower in warmer climates due to the lower energy cost for heating and temperature control.
Read more about: How To Cool Down A Fish Tank In Summer
Feed Conversion Ratio and Growth Stage Dictate The Rate Of Growth
In aquaculture, practitioners prefer a lower Feed Conversion Ratio (FCR). This translates to less fish feed per weight of fish gained. According to USAID and most practitioners, as fish mature, their FCR tends to grow higher meaning more fish feed is required to gain weight. Thus, the efficiency of growth peaks at a certain age. However, for aquaponics, as FCR is lower, this translates to less excretion for the fish. Consequently, this leads to fewer nutrients will be available for the plants. Striking a balance between this is essential for aquaponics.
Specific Growth Rate and Full Tilapia Sizes Differ Based On Climate Conditions, Source Of Fingerling, and Overall Practices
Aquaponics is based on the practice of aquaculture so we can observe growth rates comparable to standard aquaculture practices. According to research done in Teso sub-county, tilapia aquaculture has a specific growth rate of a minimum of 10kg per cubic meter per month or around 0.1 lbs per gallon.
How Big do Tilapia Get?
In growing tilapia with the intent to sell, it is important to consider the acceptable market size. This ranges from around 0.55 lbs to 1.5 lbs per fish. In natural environments, tilapia can grow up to sizes well above 2.2 lbs. However, as fish grow, their feed intake increases and their FCR increases as well, making it more inefficient to grow the fish.
How Fast Do Tilapia Grow?
Tilapia grows in ranges anywhere from 0.01 lbs to 0.1 lbs per month.
The average time until harvest for tilapia is anywhere between 5 to 6 months for small market sizes of 0.55 lbs. However, this could reach anywhere around 15 months for larger market sizes of 1.5lbs. The market value for tilapia off-market size is usually lower. Additionally, it requires more processing to get into the market. Otherwise, it is also common to sell live tilapia in tanks as these can be considered fresh and command a higher value.
In order to ensure that the system is designed to reach your market’s acceptable size, it is best to work backward in designing your system.
Is Growing Bigger Fish Better?
Maintaining the balance between aquaculture and hydroponics is key in aquaponics. Having your fish grow in biomass leads to higher feed consumption. Consequently, this leads to more nitrogen in the system which might be in excess of what your plants need. A lot of aquaponics practitioners and even experts have fallen into this trap causing fish kills in their system. As you harvest fish from the system to be sold, you reduce the source of nitrogen for your plants. This causes fluctuation of nitrogen in the system leading to nutrient imbalance.
To reduce nutrient fluctuations within your aquaponics system, keep a consistent biomass load for your aquaculture unit.
Tilapia is a significant aquaculture product in the global food supply chain. In aquaponics, tilapia remains a popular choice for growers due to its survivability and overall market acceptance. As a grower, it is best to choose what product is accepted by the market. The most important factor in deciding your aquaculture practice is the intent of growing. Larger fish sizes will give you more meat and fewer bones. This makes it easier to consume larger fish and create fillets. On the other hand, areas that prefer cheaper and smaller sizes of fish make for an accessible source of protein around the globe.