What to feed your fish in aquaponics while maintaining an exponential growth rate?
Fish in aquaponics eat a variety of food including commercially available options, homegrown bugs or plants, or homemade organic remedies. Many of these foods can easily be made from things in your own aquaponic system.
What Kinds of Food can Fish in Aquaponics Eat?
Aquaponic fish can be fed many different foods, as long as it complies with their diet, whether they are a herbivore, omnivore, or carnivore.
Common types of foods include premade, store-bought fish food, algae such as spirulina, insects, feeder or fry fish, homemade fish food and fruits and vegetables with high nutrient content.
Herbivores are happy with many of the vegetables you grow right in your aquaponic system, just ensure that the pieces are appropriately sized for the fish.
While these fish subsist almost entirely on plant matter, they are known sometimes to consume a small amount of animal protein, especially if it’s already combined with their food.
Some of the most common foods for herbivore fish in aquaponics are leafy greens, peas, chard, zucchini, duckweed, fruits such as apples, and algae.
Omnivores eat both plants and insects (or meat), and as a result, they can be reasonably easy to feed. They’ll often be satisfied eating a combination of the foods you’re already going to be feeding your other fish.
With that in mind, these fish still tend to consume more plant than animal matter. Their food will consist of up to 80% plant sources, and around 20% to 40% of food sourced from animal protein.
For omnivorous aquaponic fish food, the most popular options include algae (spirulina especially), worms, duckweed, chard, kale, other green vegetables, water beetles, insect larvae, and water plants.
We have experimented with products similar to spirulina. We always find ourselves going back to spirulina, here’s our reason why.
Carnivores are going to subsist mainly on insects and other, smaller fish or fish fry. Many of these can be either harvested from your own backyard or aquaponic system, although they’re also often available for purchase at stores. Carnivorous fish in aquaponics are likely to eat some plant matter in their diet, with up to 40% of their diet coming from plants and veggies.
To feed carnivorous fish in aquaponic systems, some of the most common options are mayflies, worms, fry fish, minnows or other small fish, insect larvae, flies, caterpillars, and other aquatic insects.
Maintaining Proper Nutrition During Massive Growth Cycles
There’s a balance you have to meet when your aquaponic fish are in the midst of exponential growth. Overfeeding can cause water quality issues that can negatively impact your system, and underfeeding can put a halt to burgeoning growth.
That said, fish are creatures that can survive off little food for quite a while, but it’s better to get a good grip on feeding amounts than not. Once your tank is really getting off the ground and has cycled (meaning you’re a couple of months in and the water has cleared up), you’ll begin feeding your fish more frequently.
While the first couple of months will consist of small, once daily feedings, the amounts of food you give your fish, as well as how frequently you feed your fish will increase.
It’s crucial to pay attention to your fish when you feed them, especially when you’re getting into a significant growth cycle.
If you’re feeding them the correct amount, your fish should be eating just about all of the food within 5 minutes. If they finish significantly faster than that, add slightly more food next time.
You can continue increasing the amount of food in small increments until you find the ideal amount of food for your fish.
Next, you’ll need to increase the frequency with which you feed your fish. Just like with adjusting the amount of food, you’ll need to do this gradually to determine how often your fish need to be fed.
Start by increasing feeding to twice daily, trying to keep your feeding times consistent. As you continue this routine, your fish will begin to expect when you’ll feed them, and as a result, you’ll get a more accurate idea of how they’re eating.
You may need to increase feedings to three times daily, but pay careful attention and ensure that your fish are actually hungry and willing to eat. Larger tanks and those experiencing a significant amount of growth may even temporarily implement the third feeding when needed.
Note: If you’re looking for a right starting place to begin testing out how much food to give your aquaponic fish, you can start giving them about 1 tsp of fish food per 20 fish, and adjust the amount as needed.
How to Provide Food for all Types of Aquaponic Fish
Aside from nutritional content, there are other things you need to consider when you feed your aquaponic fish. Like there are different kinds of fish, there are various ways that fish eat.
Some fish will come to the top of your aquaponics tank when you put food in, and they’ll eat it off the surface of the water. Bottom feeders, on the other hand, need special consideration: namely, sinking food.
As we just mentioned, bottom feeders need sinking food just as much as top feeders need floating food. Although bottom feeders, like catfish, can eat some of the uneaten floating food that sinks to the bottom, it’s not going to be enough to sustain them for long.
When you make your own fish food paste at home, make sure pellets are compressed tightly enough that they’ll sink to the bottom within 30 seconds or so. Bottom feeders can take a little longer to get their fill, so if there’s any uneaten food after 30 minutes, you can remove it with a small net.
Top feeders are a lot easier to satisfy since many fish foods naturally float (at least for a certain period of time).
The thing to keep a light eye on is that the fish food is floating for long enough for even the slower top feeders in your tank to be able to get their food from the surface. That said, many species that are typically top feeders will adapt to food in other locations over time.
Crayfish are the oddballs of aquaponics systems thanks in part to their specific (or rather lack of) eating habits, as well as their general disposition (tanks with crayfish also often have to use extra filters).
These creatures are omnivorous, meaning that they’ll eat plants, meat, even fish or plant detritus, and just about anything else they can digest. That said, you still can’t feed them anything they can swallow.
Crayfish easily take to flake or pellet fish foods and vegetables, but they’ll also munch on creatures like worms, snails, or other fish when possible.
How to Make Homemade Fish Food for Aquaponics Systems
When you’re feeding your fish, you have several options, and a combination of food sources is the best choice. A great option for feeding your aquaponic fish is with homemade fish food pellets or tablets.
You can also use food from your aquaponic system, or insects that you gather or raise yourself.
Making Fish Food Pellets or Tablets
DIY fish food can be made with a variety of ingredients tailored to the specific needs of your fish. It doesn’t take long to make your own fish food either, assuming you’ve grown, harvested, or otherwise obtained all the ingredients you need. Here’s a basic rundown of how to make your own fish food pellets or tablets:
Gather your ingredients, and ensure everything is dried out (and no longer moving if you’re using animal proteins). Portion out ingredients appropriately to ensure your fish are getting optimal nutrients.
Blend ingredients together (using a vegetable processor or similar appliance), and make sure that your ingredients have a uniform consistency. When you begin blending your ingredients, you’ll need to add a small amount of liquid (typically water or vegetable juice) and continue to add more as you blend. You want to aim to get the consistency of a thick paste or dough.
The next step will take the longest: drying out our fish food. Spread your paste-like mixture onto wax or parchment paper on a cooking sheet and preheat your oven to about 175/180 degrees. Once your oven preheats, put the sheets of fish food in to bake and dry for about 30 minutes, or until well dried. Spray occasionally with olive oil.
Alternatively, you can use an extruder or pasta press to create small tubes of the fish food paste and chop into small pellets for easier use later.
Next, all you have to do is allow the fish food to cool thoroughly and then divide it into appropriately sized pieces. You can save any extra food in a sealed bag and put it in the freezer to keep it for later use. If stored properly, your DIY aquaponic fish food should keep well for up to a year.
You can also use gelatin (unflavored and unsweetened) for easy DIY fish food at home. You’ll be primarily using the same ingredients as you would if using the method above to make your fish food. In this case, you’ll want to be sure to lightly steam any veggies that won’t easily break down, like carrots. You’ll blend the ingredients and mix with the gelatin before freezing.
Here’s an example recipe for omnivorous fish you can use to guide your own creations:
¼ c. spirulina powder
16 oz green peas
16 oz spinach
6-8 oz salmon
1 tsp garlic powder
8 oz baby carrots
4 packets unflavored gelatin
After gathering your ingredients, steam and soften any vegetables. Aim to get them tender, but avoid overcooking them to the point of getting mushy.
Blanche in ice water and set aside.
Thoroughly combine your powdered ingredients, except for the gelatin (i.e., mix up the spirulina powder and garlic powder) and set them aside.
Then take the salmon, and cut into thin strips and cubes before blending with a food processor. Set the salmon in a separate bowl.
Thoroughly blend the vegetables, and begin mixing with the salmon. After these reach a uniform consistency, you can begin adding in the mixture of spirulina and garlic powder.
Add these in gradually, making sure they’re dispersed through the mixture evenly. If the food paste is too thick, you can slowly add in small amounts of water (for the health of your fish, it’s recommended to use distilled water rather than a tap).
After the mixture is thoroughly blended, you can heat it in the microwave (but not too hot!). The goal is to make it just warm enough to be more easily mixed and help the gelatin set (you’ll notice after heating the fish food paste will seem thinner).
Slowly add gelatin to the bowl with your blended ingredients, and stir by hand. You can experiment with consistency, adding up to 4 packets of gelatin if needed.
For easier portioning and storage, you can pour your finished fish food mix into clean ice cube trays rather than a large, lined tray. Allow the trays (always cover your trays to prevent contamination) to sit in the refrigerator to set the gelatin and solidify the food, waiting up to 12 hours before removing for use.
Seal the majority of the fish food in freezer containers and store frozen for up to a year, taking out fish food and defrosting it as needed.
Here’s our guide to help you make your own fish food for bottom feeders as well as top feeders:
If you mix your fish food paste by hand (in the final stages, of course), you won’t create many air bubbles in the food. As a result, your fish food will sink, making it an ideal food for bottom feeders.
On the other hand, if you use an electric mixer or food processor for the final blend before setting, you’re going to have a lot more air bubbles in the fish food. Because of the air bubbles trapped in the finished mix, the food will float, and as a result, it’s ideal for top feeding fish.
Growing or Harvesting Insects
If you have your aquaponic garden set up outdoors (think of a backyard rig), then you’ll find yourself at an advantage here. Hence, a double benefit since you can get rid of pests nibbling on your plants and use them as a cheap, protein saturated food for your fish.
If you see an insect on a leaf, you can use a light card or soft brush to sweep them off the plant and into a container.
Many people with aquaponic systems prefer to grow or harvest their own insects to feed their fish. If you want to grow your own insects for fish feed, you’ll need an appropriate container that allows you to keep insects inside, while also allowing for sufficient ventilation and space to feed the insects.
Another way to gather, or harvest, insects to feed your fish is by catching them. While you can try and catch them by hand (or grab the occasional crawler that catches your eye), it would be a struggle to get a large amount for the effort. Instead, there are plenty of tools you can use to attract and trap insects.
A light with a higher UV output will be more attractive to insects and allow you to gather significantly more. Other tools are marketed as insect or flycatchers, although you can get creative with a DIY insect catcher.
Top feeders can easily snatch insects off the surface of the water, so live feeding is generally okay, and many fish species enjoy catching their food. Frozen insects can also be used as a supplement to their diet, although freeze dried insects should be used sparingly to avoid creating digestion issues for your fish.
Using Plants From your Aquaponic System to Feed your Fish
Herbivores and omnivores take to fruits and vegetables easily, and it’s a great way to use your aquaponic garden to sustain itself. Duckweed isn’t difficult to grow, and it is a fast-growing plant at that.
With duckweed, you can pluck it right from your system, allow it to dry thoroughly, and then feed it to your fish. Because duckweed has a tendency toward massive growth and may diminish the amount of light and space allocated to other plants, some people have a specific grow tray just for duckweed, which is kept separate from the other plants.
You can feed your fish spinach using the same process, as well as lettuce and kale or other leafy greens.
Tip: Just like when you’re making fish food using your oven, you can lay leafy greens flat on a tray and bake them in your oven at low temperature to make it faster and easier to dry them out. Keep a close eye on them so you can avoid a burnt mess. Using this process, it’s much easier to get veggies to a consistency that can be fed to your fish in a flake form.
Other plants you can grow and feed your fish include peas, zucchini, green beans, and even others you wouldn’t expect, like grapes. If you’re going to feed your fish produce, make sure that it’s treated properly and chopped into pieces small enough for your fish to eat.
That means you may need to steam harder vegetables like zucchini, carrots, or broccoli before your fish can eat them.
What does Good Fish Foods Need to Contain?
Whether you’re making your own DIY aquaponics fish food or purchasing a store-bought option, there needs to be a specific nutritional value in your fish food. The most significant things you’re going to be looking at are Protein and Fat content.
As a general rule, fish food should contain about 30% protein and only about 6% crude fat.
Of course, there needs to be sufficient iron, calcium, etc., but these nutrients are far easier to give your fish, especially when you supplement their food with produce from your aquaponic garden.
Now, if you’re looking to help give your fish a little boost in their growth, there are ways to do so without overwhelming your system with extra food or giving your fish too much of certain vitamins (which can lead to overdose or adverse health effects).
Spirulina is a favored supplement in fish food, and you can use it to assist with maintaining a high growth rate. Since spirulina is very easily digested by fish (up to 84% digestible) and contains up to 70% protein, fish get the most protein for the amount of food they consume.
You can purchase commercial spirulina fish foods, or if you’re making your own fish food, add extra spirulina powder to the mix.
Just like with spirulina, you can get commercially manufactured vitamin supplements. If you’re making your own fish food, you have a few options. First, you can grind up between two and three multivitamins into your fish food and process the fish food paste as usual.
Another opportunity to boost the vitamins in your fish food is by using baby food when you make it. Rather than adding water, mix the other ingredients as usual and use a jar of heated veggie baby food to mix into the paste and gelatin.
Do I have to feed my aquaponic fish organic food? No, you don’t have to feed your organic fish food. That said, many aquaponic gardeners prefer using organic fish feed (or homemade feed) to reduce contaminants and improve the quality of the food their system produces.
Can I keep carnivorous fish with other species in my aquaponics tank? It’s possible to keep them with omnivores or herbivores, although you still have the risk of the carnivores eating other fish, or cannibalizing their species. For minimal issues separate the tanks or remove smaller fish until they reach a proper size.