The growth rate of tilapia is determined by several factors and it is important to take all these factors into consideration. The growth rate will for instance be affected by water quality, temperature, oxygen levels and the general health of your fish. The type of food you provide them with and in which quantities will naturally also be of imperative importance. Last but not least, you have to pick an optimal stocking density.

In addition to this, it is important to choose a species, hybrid or strain that is fitting for your particular fish farm. Many producers advertise about strains with a super-fast growth rate, but this growth rate will not be attained unless the environment is ideal for that particular strain. You must for instance take the climate in your part of the world into account and the salinity level in the water you plan on using is also important.  

Mixed-sex or mono-sex culture?

When male and female tilapias are kept together, they will readily breed and produce a lot of offspring. This can hamper the growth rate of the adult fish, since they will be forced to compete for food with fry and fingerlings. Three methods are commonly utilized to prevent this from happening.

1. Harvesting the mix-sexed culture before they reach sexual maturity or soon afterwards.
2. Raising the mix-sexed culture in cages or tanks that disrupts preproduction.
3. Raising a mono-sex culture consisting of males only.

Growth rate in mixed-sex culture

In a mixed-sex tilapia culture, the fish is normally harvested before the fish reaches sexual maturity or soon afterwards. This restricted culture period makes it even more important than normally to make the fish grow fast, since they have to reach their proper size within a limited time frame. It is therefore common to avoid dense stocking of mixed-sex tilapia cultures. It is also important to avoid using stunted fish since such fish will reach sexual maturity while they are still too small for the food market.

Blue tilapia (Oreochromis aureus), Nile tilapia (Oreochromis niloticus) and their hybrids are common in mixed-sex cultures since they will attain a marketable size before commencing spawning. Species such as Mozambique Tilapia (Oreochromis mossambicus) and Wami tilapia (Oreochromis urolepis hornorum) are normally avoided since they will be too small when they reach sexual maturity.

By choosing the right species or strains and providing the fish with a suitable environment and proper nutrition, it is possible to achieve a growth rate fast enough to allow fry produced in the spring to reach a marketable size by autumn in temperate regions. For a 4-5 month long culture period it is common to stock 2,000-6,000 one month-old fry per acre in growout ponds. With a stocking density of 4,000 fry per acre, the average weight at harvest can then be expected to be around 0.5 pounds (220 grams), if supplemental feedings with protein rich food has been carried out.

Growth rate for all-male fingerlings

In mono-sex cultures, it is common to opt for male fish only since the male tilapia grows faster and reaches a larger size than the female. All male batches can be obtained through hybridization, hormonal treatment or manual sexing and separation. It should be noted that none of these methods can guarantee 100% males in any batch. If you want really large tilapia, the amount of females in the growing unit should not exceed 4 percent. Many farmers therefore use more than one method to ensure a low degree of females in the growing unit. Predator fish of a suitable size can also be added to the growing unit to devour any offspring.

All-male tilapia cultures are often densely stocked. This will decrease the individual growth rate of each fish, but it will normally result in a higher yield per unit area. Densely stocked cultures are more susceptible to ill-health and careful water management is recommended, since poor health can have a devastating effect on growth rate and lead to massive losses.

The normal stocking rate for all-male tilapia cultures varies from 4,000 to over 20,000 fishes per acre. If you have no supplemental aeration, it is safest to stay in the lower range. In a suitable environment with an adequate supply of nutrition, it is possible for 50 gram fingerlings to become 500 gram fishes within 6 months even without supplemental aeration if the stocking rate is 4,000/acre. This means an average growth rate of 2.5 grams per day and it is possible for such a culture to yield 2.2 tons/acre.  

A stocking rate of 8,000/acre can yield up to 4.4 tons/acre, but will require night time emergency aeration. You can expect the average weight gain to be 1.5-2.0 grams/day. The culture period will need to be at least 200 days, often more, if you want to produce fish that weighs almost 500 grams.

Stocking rates above 12,000/acre will require extensive aeration, but can on the other hand yield up to 6-10 tons/acre. Keeping the water quality up will be difficult and you might have to resort to sub-optimal feeding rates and this will naturally affect the growth rate.