Which fish to choose for aquaponics ?

Goldfish are arguably the most commonly used species in aquaponics. They can live in a small tank and withstand significant temperature fluctuations. Hardy and highly tolerant, they adapt well to temperate or cold waters.

Larger koi are ideal for outdoor ponds and add an aesthetic touch with their vibrant colors. These fish are not intended for consumption, but they effectively contribute to the nitrogen cycle by producing nutritious waste for plants. Just be careful not to overcrowd the pond to maintain clean water (using good filtration and regular water changes helps maintain balance).

For very small systems or aquariums dedicated to aquaponics, you can turn to small tropical fish . Guppies, for example, are very hardy and easy to raise livebearers. They reproduce quickly, which can be interesting to observe. These livebearers can adapt to cooler waters and can generally remain outdoors from April to October. However, you will need a fallback solution for the winter.

Although their nutritional impact is less significant compared to plants, they are a fun and educational choice for beginners. Other aquarium fish such as bettas, gouramis, ancistrucs, and some cichlids can also be suitable in this context.

Rainbow trout are prized for their fine flesh and rapid growth. They require cool, well oxygenated water (10 to 18°C), making them ideal for systems with fine temperature and aeration control, but complex to maintain in summer.

Pikeperch , a noble fish also appreciated in gastronomy, withstands more variable temperatures and remains relatively tolerant. Less common in aquaponics, it represents a great opportunity.

Finally, common carp , like koi carp, are distinguished by their robustness. Omnivorous, they adapt easily to aquaponic systems. They are perfect for simple systems, especially outdoors or for food self-sufficiency.

The right choice will depend on your local climate, your goals, and the technical constraints of your aquaponics system.

Tilapia is the flagship species of tropical aquaponics. Easy to raise, requiring little oxygen, and highly resistant to variations in water quality, it thrives between 22 and 30°C. Its rapid growth and easy reproduction make it a strategic choice for large-scale production.

The African catfish , on the other hand, tolerates extreme conditions, including oxygen-poor waters. It is carnivorous and grows rapidly, making it a profitable species for well-balanced systems.

The Nile perch , which is larger, is suitable for large ponds. It offers highly prized meat, but requires good water management and a specific diet.

Not all species coexist well together : some are aggressive, while others are overly sensitive or stressed in the presence of different species. Additionally, their temperature, oxygen, and food requirements may be incompatible. For example, it's risky to keep goldfish with tilapia, or trout with exotic fish.

If you want to introduce several species, choose fish of similar size, with peaceful behavior, and similar living conditions (example: Koi carp and goldfish).

It is often easier to stick with one species per system to ensure stability and ease of maintenance.

Choose a quality fish food that's appropriate for the species you're keeping. For example, protein-rich pellets for carnivores like trout or catfish, and plant-based pellets for omnivores like tilapia or carp.

Generally, it is recommended to distribute small amounts of food once or twice a day, which the fish can consume within a few minutes. Remove any leftovers with a net to avoid polluting the water.

A well-balanced diet promotes fish growth and limits waste production, which relieves the strain on the filtration system and keeps the water cleaner.

Fish density is a fundamental parameter in aquaponics. Too many fish = excess waste, water pollution, stress, and disease. Too few = lack of nutrients for plants.

In home aquaponics, the balance is often around 15-20 kg of fish per cubic meter of water , but this depends on the type of fish, filtration and the quantity of plants grown.

Always start with a moderate stocking density. Observe how nitrate levels and the condition of the fish evolve. If the plants are lacking nutrients, you can gradually increase the population. When in doubt, fewer healthy fish are better than too many suffering animals.