In this article, we are going to discuss how to maximize the fish mass produced in relation to the kilos of food provided in aquaponics. First of all, you should know that in aquaponics, this accounts for between 40 and 50% of our expenses. It is also important to understand the growth curve of fish. We all know that at the beginning, the fish is very small. Let's take the example of koi carp, which do not gain much mass until they are one year old, but between one and three years old, the slope of the curve will be very steep, and therefore the fish will gain a lot of weight in a short time. Afterwards, there will be a clear inflection for the rest of its life.

Why is there strong growth at the beginning and then significant stagnation?

This is mainly linked to the production of reproductive sex cells, male or female. In fish, these are called gametes. The male gamete is the sperm produced by the testicle. The female gamete is the egg produced in an ovary. Thus, the sexual maturity of females is different from that of males. For koi carp, this will be 4 to 5 years for a female and 2 to 3 years for a male.

We are going to take a well-known example in aquaponics, which is the rainbow trout, because we like to raise them in our aquaponic tanks, especially in cold climates. You should know that for this species, the sexual maturity of males is at one year, while that of females is at two years. So basically, we will have an optimal growth for a given amount of food for one year for males and for two years for females. In fish farming, they only want to raise female trout since that is when they get the best yield. This leads them to perform aberrations such as giving male hormones to small females. As a result, the small female trout will develop testicles and will have the phenotype of a male, but the genotype of a female. And so it is a pseudo-male and a female that will produce exclusively females since all the chromosomes will be X.

So if you buy trout from a fish farm, in 99% of cases, they will be females since that is how we get the best growth for the minimum amount of food provided.

A few basics to ensure fish grow well

The first thing is that the water temperature must be suitable for the species. You wouldn't put tilapia in cold water or trout in warm water. Next, you should provide food adapted to the species you are raising. There are herbivorous fish, carnivorous fish, and omnivorous fish that eat both. So, be very careful and make sure to buy the food that is suitable for your fish. And finally, you need a sufficient quantity of food for them to grow. You must cover the energy requirements for their metabolism and their cells for their activity. So, if you give them a few pellets once a week, they will survive. But obviously, they won't grow.

The difference in terms of growth

The first thing to know is that fish will grow faster if you feed them several times a day. So, for a daily dose of food, it is better to split it into two or three feedings, rather than giving it all in the morning or evening. Then, to optimize the growth of all your fish, they will need to be roughly the same size.

In fish farming, they spend their time grading the fish, that is to say separating the small ones from the medium and large ones, not only so that they don't eat each other, but also so that everyone can absorb the right amount of food, and not just have the big fish eat all that is available for the small ones.