Aquaponics incorporates aquaculture and hydroponics in a food production system resembling a natural ecosystem. Most aquaponics farmers rear freshwater fish, including tilapia, catfish, trout, jade perch, or ornamental fish. Now, if you’ve just ventured into this form of integrated agriculture, you might want to figure out how to feed your aquaponic fish.
When feeding aquaponic fish, it’s crucial to identify their dietary needs, provide nutritionally balanced food, and stick to a schedule. You should also factor in your plants’ nutritional requirements and use a practical formula to determine the ideal portion size.
Properly feeding your aquaponic fish will ensure that you also meet your plants’ nutritional needs and maintain a viable ecosystem balance. So, let’s get into the details and discuss how you should feed your aquaponic fish to ensure that your system flourishes.
How To Feed Your Aquaponic Fish
Following some steps will help you develop a routine when feeding your aquatic friends, ensuring that you have all of your bases covered.
So, let’s go through the process together:
1. Identify the Dietary Needs of Your Aquaponic Fish
Different fish breeds have varying nutritional requirements. So, the type of feeds you’ll choose for your aquaponic fish will depend on their breed (and species). For instance, some fish breeds, including Bass and Trout, require high protein content in their diets.
You can incorporate herbivorous, carnivorous, or omnivorous fish into your aquaponic system. However, meeting the protein requirements of some carnivorous fish breeds can be an uphill task. Hence, most farmers who practice aquaponics prefer rearing fish breeds that are easy to feed and good for food.
Now, let’s look at common fish breeds reared in aquaponic food production systems and their dietary needs.
Tilapia
Tilapia is one of the most sought-after fish breeds for aquaponics, as they’re easy to breed and maintain.
This fish breed adapts to varying environmental conditions and can live in crowded ponds. Moreover, they are large-sized fish and a popular delicacy in many countries globally. Though tilapias can live in environments with a 3.7 to 11 pH range, their most favorable water pH is 7-9. Also, their preferred temperature range is 22-29°C (71.6-84°F).
Dietary needs: Tilapias are primarily herbivores but can adopt an omnivorous feeding behavior depending on their habitat. Their nutritional requirements include:
- 40% protein
- 5% carbohydrates
- 8-12% lipids (for tilapia weighing up to 2.5 g or 0.9 oz)
- Many vitamins and minerals
Get more information here on the recommended amounts, depending on the tilapia species and size.
Rainbow Trout
Rainbow Trout are a common fish breed in aquaponic systems, as they’re hardy and tasty. However, it’s not advisable to keep them if you’re a beginner since they have more maintenance requirements.
Moreover, Rainbow Trout are recommendable if you’re growing vegetables, including broccoli, cabbage, and cauliflower. Trout prefer cold waters of about 12°C to 15°C (53.6°F to 59°F), as they require high dissolved oxygen levels.
Dietary needs: Trout are carnivorous and feed on small fish. However, they can also feed on fish pellets. They require approximately:
- 35-45% protein
- 12% carbohydrate (maximum)
- 1% lipids (minimum)
- Vitamins
- Minerals
Channel Catfish
These are other commonly reared fish due to their fast growth rate. Catfish thrive in high temperatures and pH levels between 5 and 7. Also, they’re an excellent fish to breed for aquaponic newbies, as they can adapt to various environments.
Dietary needs: Catfish are bottom feeders that feed on worms, pellets, zooplankton, and algae. They require about:
- 22-55% protein
- 25% digestible carbohydrates (and 3-6% crude fiber)
- 0.5-0.75% lipids (essential fatty acids)
- Vitamins
- Minerals
Yellow Perch
Yellow Perch is a good choice if you’re looking for edible and fast-breeding aquaponic fish. They thrive in cold waters, with temperature ranges of 18°C to 25°C (64.4°F to 77°F) and 6.5 to 8.5 pH levels.
Dietary needs: Yellow perch naturally feed on invertebrates and small fish, but they can also consume fish pellets and vegetables. Their recommended nutrition profile includes:
- 36% protein
- 10-15% lipids
- vitamins (especially vitamin C)
- Minerals
Koi and Goldfish
These fish are mainly reared as ornamental fish in ponds and aquaponic systems. Koi and Goldfish are omnivores and usually feed on insects, aquatic plants, and fish pellets.
Goldfish are edible, but they aren’t among the tasty fish breeds. They also thrive better in large spaces. On the other hand, Koi aren’t edible. However, they are still popular in aquaponics due to their appealing look and adaptability to varying environmental conditions.
Dietary needs: The two fish breeds have almost similar nutritional requirements. They consume about:
- 30-40% protein
- 11-12% lipids (mainly omega-3 fatty acids)
- 10% carbohydrates (maximum)
- Vitamins
- Minerals
Knowing the dietary needs of different fish species will also help you decide which fish to rear in your aquaponics farm. However, apart from nutritional deficiencies, here are other factors to consider when choosing fish species for your aquaponics system:
- Size and space: determines your fish stocking density, the amount of feed to use, and the type of plants to grow.
- Breeding habits: some fish breeds, such as catfish, breed faster than others. On the other hand, some species don’t reproduce in captivity.
- Water temperatures: determine what type of fish you can breed, as different fish breeds have varying temperature requirements.
- Maintenance difficulty: some fish breeds have more maintenance needs than others.
2. Provide Nutritionally Balanced Fish Food
As we’ve just seen, every fish breed has specific nutritional requirements. Hence, you should ensure that your fish feed meets all the dietary needs of the fish species in your aquaponic system.
Moreover, the availability of the required food source and its ease of use are also important factors, as they’ll also determine what fish breed you can rear.
Here are the essential nutrients that well-balanced fish food should contain.
Proteins
All fish breeds require amino acids (protein building blocks), including essential and non-essential amino acids in their diet.
Essential amino acids such as lysine and methionine are some of the most crucial amino acids, and you should always ensure that your fish get these proteins.
Proteins help in building the fish body mass through structure and enzyme production. They are also a vital requirement in young fish and carnivores.
Carbohydrates
Like other organisms, fish need carbohydrates for energy, and they’re a significant component of most fish feeds, such as commercial pellets. So, energy-rich food sources, including starches and sugars, should be part of their diet.
However, some fish breeds like yellow perch and rainbow trout have minor carbohydrate requirements and survive on carbohydrate-free feeds. However, this doesn’t mean that you should exclude carbs from their diets. In most cases, these fish breeds have better health when consuming foods that contain carbohydrates.
Lipids
Lipids, or fats, are high-energy molecules that fish need for growth.
Moreover, they have a crucial role in fat-soluble vitamin absorption and feed conversion. Your aquaponic fish will have stunted growth and reproduction problems if they lack lipids, as they help produce hormones.
You’ll find fish oil in most conventional feeds, and it’s a good source of lipids. The oil primarily contains two types of fatty acids, omega-3, and omega-6 that are also nutritionally beneficial to humans.
Vitamins and Minerals
Vitamins and minerals are vital micro-nutrients for fish growth and health.
Vitamins are organic molecules that you’ll find in plants, including vegetables and fruits. They help in fish development and also boost their immune system.
On the other hand, minerals are inorganic elements that form cell structures and other body parts.
3. Factor in Your Plants’ Nutritional Requirements
Since aquaponics is an integrated food production system, it involves a symbiotic relationship between fish and plants.
Therefore, rearing fish is a great way to recycle wastes and utilize nutrient-rich water. Moreover, the fish breed you choose to raise in your aquaponic system should have similar environmental requirements as the plants, including the temperature and pH ranges.
Now, when you’re choosing the type of feed for your fish, also consider the kind of plants you’ll grow. Ideally, the fish feed’s nutrient profile should match the plants’ nutritional requirements.
Additionally, how you feed your fish and how many you keep in your system will also determine the number of crops you can plant.
According to University of Virginia Islands studies, if your raft aquaponics system has 10 square feet (0.93 sq m) of plants, your fish should consume about 2-4 ounces (60-110 g) of fish food daily.
On the other hand, if you’re practicing the nutrient film technique (NFT), your fish feeding rate will depend on the type of plant species on your farm. However, this amount can be between 25 and 75% of the fish food used in the raft system.
Generally, plants will require about 16 types of nutrients, some of which they’ll obtain from fish wastes (after feeding). They get the rest of their essential food from the atmosphere and the nutrient-rich water.
However, you can also supplement this with some nutrients lacking in fish food, such as potassium, iron, and calcium. Moreover, ensure that your system’s pH levels match the required levels for your plants for maximum nutrient intake.
4. Use a Practical Formula To Determine the Portion Size
Your fish food’s portion size can depend on several factors, including the species and age.
In addition, the size of your aquaponic system and the type of plants you grow will also determine the optimal portion size for your fish. Therefore, you can utilize a mathematical formula to determine the specific amount of fish feeds that you should give your fish.
One of the preferred formulas is using 20 g (0.7 oz) of fish food per square meter (11 sq ft) in a Deep Water Culture growing area.
Another formula is based on the fish’s body weight. With this method, the weight of fish food per day should be about 2% of the fish’s body weight (per fish).
An appropriate feed portion will prevent under-feeding or overfeeding your fish.
Under-feeding leads to nutrient deficiencies, diseases, and aggressiveness in fish.
On the other hand, overfeeding is detrimental to your fishes’ health and causes the accumulation of wastes, degrading water quality. So, do not overfeed your fish when the temperatures are too low, as your fishes’ metabolisms (including digestion) will be slower.
Also, avoid under-feeding during summer or when the temperatures are higher, as the fish will be more active.
So, apart from minimizing incidences of nutrient deficiency and related health complications, feeding them the right amount of food at the right time will ensure that your fish have sufficient energy.
5. Have a Fixed Feeding Schedule
Many specialists recommend feeding aquaponic fish twice per day. You’ll find these guidelines when you purchase a sachet or tin of fish pellets.
However, some argue that you can feed your fish more frequently if you have a low stocking density to provide plants with sufficient nutrients.
As mentioned earlier, in aquaponics, the symbiotic relationship between fish and plants reduces nutrient wastage in the environment. Moreover, the two follow daily rhythms (and circadian rhythms) when carrying out physiological processes, such as nutrient intake and excretion.
So, a farmer should consider following a strict routine when determining the most appropriate fish feeding schedule.
According to various studies, plants show circadian rhythms by taking in nitrogen (and nitrates) at night. In the same way, fish excrete nitrogenous wastes at specific times, depending on their feeding times. For instance, diurnal fish (active during daytime) feed well during the day while nocturnal fish feed at night.
Hence, it’s crucial to be aware of these circadian rhythms in your aquaponics system and match your feeding schedule accordingly. Doing so will ensure that your plants will take in the nitrogenous wastes from the fish right after they eat.
So, feeding your fish when the plants need nutrients most will also boost your system’s performance and lower maintenance costs.
Another factor to consider during your feeding schedule is the feeding duration. Most fish species feed actively within the first five to ten minutes. After that, they will retreat, leaving uneaten food either floating on the water or at the bottom of the tank.
It is best to remove the remaining feed about five minutes after your fish have eaten. Doing so will keep waste out of the tank and help you maintain water quality without frequent cleanings.
6. Monitor Your Aquaponic Fish Feeding Habits
Different fish breeds have different feeding habits. Also, various feed types may positively or negatively affect your fish. So, keeping track of their feeding behavior will help you budget their feeds and find what works best.
You can determine the impact of specific fish food by assessing the fish’s growth and performance.
For instance, the feed conversion rate (FCR) determines the amount of food you need to feed your fish to obtain a specific amount of growth. If a 50 g (1.8 oz) fish gains 7 g (0.25 oz) after consuming 14 g (0.5 oz) of fish food in one week, the FCR will be 2.0 (the amount of food divided by the net gain).
Calculating the FCR will determine if your fish have been eating well. Additionally, it will help you assess if the type of fish food is viable for fish growth and performance.
Following these calculations can also help determine if the input cost is higher or lower than the output. So, feeding your fish wisely can raise profits and eliminate unnecessary waste.
If your fish are not doing well after consuming a particular fish food, seeking an alternative is the best option. However, other factors, including environmental conditions, may also affect fish feeding habits.
Some factors that may have an impact on your fish’s feeding habits include:
- pH
- Water temperature
- Dissolved oxygen
- Ammonia, nitrite, or nitrate levels
Hence, it’s advisable to frequently test these parameters, especially when setting up your aquaponics system. Some home testing kits are available, and they help determine the quality of the water.
Best Foods for Aquaponic Fish
High-quality fish food should be nutritionally balanced to meet the dietary needs of your fish.
You can either purchase the conventional feeds from your local pet store or prepare the food at home. However, homemade fish food can lack the essential nutritional components if you don’t follow the tried-and-true formulas.
For beginners and small-scale aquaponic farmers, commercial pellets are the best option. However, depending on the fish breed, these feeds may be costly or scarcely available depending on the fish breed.
So, if you’re an experienced farmer, preparing homemade food can be a good alternative, but you should also consult nutritional experts.
Here are some of the best food sources for aquaponic fish:
Fish Pellets/Flakes
Most fish food manufacturers combine the required nutrients into pellets, depending on the species’ dietary needs.
Fish pellets come in various sizes (2 to 10mm or 0.08 to 0.4 in) and sink in water for fish to swallow them easily. However, the uneaten ones can diminish the water quality.
On the other hand, flakes are pellet-like feed that floats on water. Although they don’t affect water quality much, your fish can develop health complications if they gulp in the air when feeding on the flakes.
Be sure to get high-quality fish food, as this will reduce the buildup in your aquaponic system.
Insects and Worms
Insects and worms come in handy when you supplement your fish diet. Most grubs, including earthworms, crickets, soldier flies, cockroaches, and wingless flies, are a rich protein source. Another advantage is that you can easily rear them on your farm at minimal costs.
Aquatic Plants
Growing aquatic plants in your pond is cost-effective since it will help you meet your fishes’ dietary needs. Aquatic plants are incredibly convenient if you have omnivorous or herbivorous fish in your setup.
Aquatic plants, including algae, zooplankton, duckweed, and water lettuce, are viable supplements to fish pellets.
Duckweed, a fast-growing aquatic plant, is mainly a favorite for tilapias, and it also helps in recycling nutrients and has high protein content.
The only downside with aquatic plants is their tendency to clog pipes and filters often used in hydroponics.
Moreover, they can also deprive your fish of oxygen or lower the water quality upon decomposition when you let them grow on the water’s surface. So, it’s best to push the plants down to the tank’s substrate and keep them off of the top of the water.
Now, here are the conditions to maintain when planting duckweed in your aquaponic farm:
- The pond water should be 8 inches (20 cm) deep.
- Water temperatures should be between 50 and 90°F (10-32°C).
- Keep the pH range at 6.0 to 7.5.
- Harvest your duckweed every two weeks – you can also freeze it until the next feeding session.
Garden Plants
If you’re growing some veggies or fruits in your backyard or tank, you can also feed some to your herbivorous and omnivorous fish.
Fruit slices, including watermelon, apple, and oranges, are rich sources of vitamins. These can supplement their diet if you’ve been feeding them on fish pellets, though some species may take time getting used to this combination.
Small Fish
Rearing carnivorous fish (such as trout and bass) in an aquaponic system isn’t ideal for beginners, as these breeds require protein-rich diets.
Still, plenty of fish foods and supplements with a high protein content will help you meet these nutritional requirements. However, if they aren’t readily available in your area, you can opt to feed your fish on smaller (bait) fish and minnows.
Conclusion
Fish feeding is one of the most crucial aspects of aquaponics. The type of fish food to use primarily depends on the dietary needs of the fish breed. In addition, the plant species in the system is also a vital factor to consider.
Therefore, to properly feed your aquaponic fish, do the following:
- Know your fish’s dietary needs.
- Factor in the plants’ nutritional requirements.
- Use a formula to determine the portion size.
- Have a fixed feeding schedule.
- Monitor your fish’s feeding habits.
