Fish are Friends: Aquaponics for Home Gardeners

Remember Bruce, the great white shark in the Disney Pixar movie Finding Nemo? He famously declared that fish are friends, not food to keep his predatory nature in check and not chomp down on his new fish pals, Nemo and Dory.

Whether you’re more like Bruce — preferring to watch salmon than snack on them — or you’d just as soon have a tuna sandwich for lunch, if you’re interested in aquaponics gardening, fish are definitely your friend. In fact, without them, aquaponics wouldn’t work. 

Waste in, clean water out

Aquaponics is a method for growing fresh produce and fish together in a sustainable, closed-loop system. In this case, closed loop means the waste from the fish provides nutrients for the plants, and the plants help to filter the water for the fish. 

In general, here’s how it works:

1. Fish in the tank produce waste, primarily in the form of ammonia.
2. Beneficial bacteria that colonize the grow bed (where the plants are grown) break down the ammonia and convert it to nitrites and nitrates, essential nutrients for plant growth. 
3. Nutrient-rich water from the fish tank is pumped through the grow bed to the plants’ roots.
4. The plants remove harmful toxins and impurities from the water, which then returns to the fish tank.

There are no chemical pesticides or herbicides involved, plants grow faster than their soil-bound counterparts, and no fish are harmed in the making of a great garden.  

In fact, aquaponics is a fun way for the entire family to learn about how plants and fish interact with each other. Even the environment gets a win in the deal: Aquaponic systems use up to 90% less water than traditional gardening methods.

How about a desktop garden?

Though there are large commercial aquaponics operations, the method is well-suited for backyard, patio, and urban gardening. However, the size of the fish, the number of plants you want to grow, and whether you’re aiming for personal consumption or larger production will all influence the size of the system and how much space it takes up. 

A backyard Nutrient Film Technique system — where plants are grown in shallow channels — generally averages 40 to 100 square feet in size, but it’s easy to go smaller than that. Some of the smaller systems use watertight plastic bins or buckets as the fish tank and various containers for the grow bed. There are even desktop systems consisting of a fish tank with a grow bed on top. 

What’s best for you will depend on your available space, budget, and experience level. 

And while there’s no question aquaponic gardening is exciting and fulfilling, there’s definitely a learning curve involved. Before you jump in, you’ll have to brush up on fish care, plant cultivation, and water quality management. 

It also takes time and effort to set up the system (assembling the tank, grow bed, and pump then adding the fish and plants) and maintain it. To keep plants and fish healthy, you have to test the water quality, feed the fish, prune the plants, and keep the entire system clean. A failure in one area can have a global effect: If the fish die because the water is dirty, there won’t be enough waste to form plant-fertilizing nutrients.

And to be honest, an aquaponics system can be more expensive than traditional gardening. But when you start harvesting produce sooner than before, you’ll see it was worth all the work. 

Grow a salad

Growing Bok Choy in an aquaponics system

While the size of your aquaponic system and the climate you live in will help determine the kinds of plants you grow, some of the best plants include:

• Leafy greens such as lettuce, Swiss chard, and kale. Lettuce grows especially quickly because it doesn’t have many nutrient requirements.
• Fast-growing basil, mint, and chives. Because basil has a lot of nutrient requirements, it’s better suited for a slightly larger system.
• Tomatoes and peppers, although they can be finicky. Keeping the water temperature constant is key.
• Cucumbers. Remember, though, their viny nature requires a lot of space.

Generally speaking, plants with deep root systems are not well-suited to most aquaponic setups.

Tip the scales

Tilapia is a popular choice in aquaponic gardens

And what about the fish? Which ones are most common in aquaponic gardens? 

• Fast-growing and hardy, tilapia are a great choice because they can tolerate a wider range of water conditions.
• Catfish not only produce nutrients but they’re bottom-feeders, meaning they help keep the system clean.
• Although barramundi are saltwater fish, they can be adapted to freshwater environments. They’re becoming increasingly popular in aquaponic gardens because they grow fast.
• Koi are most often prized as decorative fish in ponds, but they are suited to aquaponic gardens as well. They can get quite large, however, and may outgrew the system.
• Even goldfish can be helpful to the aquaponic garden, but they tend to be small and less efficient waste-producers.

Now, what about eating the fish from your aquaponic system? Is that advised? The truth is, tilapia, catfish, and barramundi all make an excellent meal and there’s no reason why you can’t pluck them from the system and serve them for dinner. But the question is: if fish are friends, not food, are you sure you want to?

While aquaponics offers a sustainable and efficient way to grow food, it does have some downsides to consider:

Initial investment

Setting up an aquaponics system can be more expensive than traditional gardening methods. This includes the cost of the system itself, the fish, the plants, and any additional equipment you may need.

Overall, while aquaponics offers numerous advantages, it's essential to be aware of its downsides and limitations before deciding if it's the right approach for you. Weighing the pros and cons and understanding the commitment involved will help you make an informed decision.