Proper fish feeding is not just important for growing valuable fish on a profitable schedule. The food for your fish is what eventually becomes the fertilizer for the plants. Low-quality feed products, uneven feeding schedules and over- or under-feeding can all lead to damage to the entire system. Profitable aquaponics systems begin with quality commercial fish food that is appropriate for the fish species you choose.

Carnivores vs Omnivores

All fish require some amount of protein and fat supplied by insects and other fish. The amount required for their diet determines whether they are carnivorous or omnivorous. Carnivorous fish food costs more because it requires more expensive ingredients and more processing steps than omnivorous pelleted or crumbled feed. However, carnivorous fish also tend to command a higher price and offer higher levels of demand from customers. Omnivorous fish need protein and fat from the same sources used in carnivorous feeds, but they simply require less of these macronutrients. This allows for more of the calories to come from plant sources that are less expensive and require less processing, resulting in more affordable feed.

Don’t just purchase fish feed in pelleted or crumble form based on its nutritional value alone. Feeds formulated for ponds and open water raceway systems lack many of the minerals and nutrients added to feeds meant specifically for aquaponics use. Even if the fish don’t need all of these extras, your plants do. Sourcing an aquaponics specific fish feed is one of the most challenging parts of starting a profitable aquaponics business. If you absolutely can’t find a formula that meets all the requirements of the plants in the system, you can add these nutrients separately as necessary, but at a much higher cost than if the nutrients were supplied by the feed alone.

Sourcing Fish Feed

Start by looking for local feed mills and aquaculture supply companies. If you find a feed mill that isn’t currently producing a feed you can use, you may be able to order a custom formulation with the exact nutrient balance necessary for both the plants and fish. Aquaculture supply companies tend to charge much more per pound than general feed suppliers, but you’ll get the right formula from the beginning and experience fewer issues. With the right formula, the system will require fewer system adjustments compared to compensating for lacking nutrients. Global companies producing aquaponics appropriate fish feeds include Cargill, AquaMax, Skretting and EnviroFlight.

Determining How Much to Feed

In general, fish in the fingerling size and above need to eat around 7% of their body weight per day at the youngest age and drop down to 4% of their body weight per day nearing harvest age. Look for a feeding chart based on the specific species of fish you choose. Fish raised in aquaponics systems require the same rates of feeding used in other forms of recirculating aquaculture, so as long as your feed rates fall within the guidelines listed in this book for proper plant growth, the entire system should function well. If you end up introducing too much feed into the system to keep up with high stocking densities, you may need to expand your crop growing surface area to compensate for the extra nutrients entering the system. Adjust your feeding rates every two weeks according to the average weight of a sample of at least 5-10 fish to ensure you’re not wasting food or underfeeding and slowing the growth rate.

Automating Feeding Routines

Hand-feeding fish may work just fine for backyard and hobby systems, but it’s too time consuming and unreliable for commercial production. Almost all commercial aquaponics businesses rely on automated feeding equipment to keep fish evenly fed, especially during the early stages during which fingerlings may require up to four different feedings a day. The automated equipment used for pond cultures is often too large to work for the smaller tanks or ponds used in aquaponics. Recirculating aquaculture feeders should work fine, as tanks are still used for these systems. Avoid homemade or improvised fish feeders; they’re too prone to failure to rely on for commercial purposes.