What Is Aquaponics?

How Aquaponics Works, Types, and Pros and Cons.

Seedlings, greens, herbs grown in aquaponics system
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Aquaponics is a crop production system that combines hydroponics—which involves growing plants without the use of soil—and aquaculture—which refers to cultivating aquatic animals like fish and crustaceans. An aquaponic system may look like a hydroponic system from above, but instead of having a main reservoir filled with a nutrient-rich solution, the nutrients will come directly from a tank of live fish.

Any plant that can be grown hydroponically can benefit from aquaponics; plants like tomatoes, peppers, leafy lettuce greens, and herbs are some of the most popular. Farmed freshwater fish are commonly used in aquaponic systems. Factors like temperatures, pH, and nutrient levels must be balanced between the plants and the animals to be successful. Most systems use tilapia, since they can adapt to a range of environments, withstand different water conditions, and are easy to breed.

How Does Aquaponics Work?

In aquaponics, the water from the fish tanks hydrates the plant roots while the fish waste provides natural fertilizer to feed the plants themselves. At the same time, the plants filter the water to keep it clean and safe for the fish. Water from the fish tank is recirculated through the system and across the grow beds full of plants, which absorb the dissolved nutrients in the water.

Using crawfish for an aquaponics system
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Aquaponics mimics the natural aquatic ecosystems found in rivers, streams, and other bodies of water, creating a symbiotic relationship between plant and animal that benefits both equally.

It sounds simple enough, but there are several other factors at play here. Between the plants, the fish, and the bacteria inside the water, there are a total of three living organisms within an aquaponic system. These organisms all have different needs when it comes to pH balance, so it needs to be monitored daily to ensure that it doesn’t become too low or too high. The fish waste may cause the pH balance in the water to become too acidic, for example, stopping the plants from absorbing nutrients efficiently and killing off everything in the system. That’s why it's important to match your fish and plants depending on factors like temperature and pH, just as mother nature would do in the wild. An aquaponic grower will also have compatible pH adjusters on hand to help maintain this delicate balance, and some may add red worms into the grow beds to help break down and evenly distribute waste to the plants.

What Fish to Use for Aquaponics?

Tilapia is the most common fish species used in aquaponics and is the perfect starter fish for novices, but growers can also use trout, catfish, bass, and even crustaceans, goldfish, or ornamental koi.

Types of Aquaponics

Like hydroponics, aquaponics requires the use of growth media rather than soil to help support the plants and protect the roots. In aquaponics, the growing media also serves as a surface for good bacteria to thrive within the grow bed and help filter the waste expelled by the fish tank. Expanded clay pebbles are a lightweight aggregate that is expensive yet efficient, but media can also be gravel, shale, and even porous lava rocks. The right media depends on the type of plant, size of the system, pH level, cost, and type of aquaponic system used.

Deep Water Culture

Also known as raft-based growing, this aquaponic system uses a foam raft that floats in a channel filled with fish tank water that’s been filtered to remove the solid waste. Within the raft, the plants are placed in holes with their roots dangling in the water in order to draw nutrients directly from the channel. This system is most commonly used in commercial operations or for growing plants that need fewer nutrients and grow quickly such as salad greens.

Media Bed

Tomato plants growing in aquaponics system using hydroponics
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This technique grows plants in inert planting media beds, such as expanded clay pebbles or shale, which sit on top of or next to the fish tank to provide plants with both biological filtration and mechanical filtration. Biological filtration refers to the conversion of ammonia (produced naturally from the fish waste) to nitrates, while mechanical filtration has to do with the removal of solid waste itself. A pump will draw the water from the tank, passing it through the media bed to let the plants draw nutrients from the water before returning it back to the tank fully filtered.

Most home and hobby scale systems are based on media aquaponics, as well as larger-scale operations of fruiting plants, leafy greens, and herbs.

Vertical Aquaponics

As the name suggests, vertical aquaponics stacks plants on top of one another in a tower. Water flows from the top through a wicking material to provide the plant's roots with nutrients before falling into a lower trough or fish tank directly under the system. It’s another space-saving method, and it allows growers to produce a larger amount of food with relatively small square footage.

Nutrient Film Technique

Aquaponics plants growing in pipes
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Also referred to as NFT, the nutrient film technique works well for plants like strawberries, leafy greens, and herbs that don’t require much support. Plants are placed in holes drilled into narrow troughs, like a PVC pipe, allowing the roots to dangle directly into the water. The systems can also be hung from ceilings or run across walls above other plants, so it is a great way to utilize space.

Aquaponics at Home

There are a number of aquaponic kits available to those who wish to try their hand at aqua farming at home, and as the practice becomes more popular the at-home systems are just becoming more convenient. If you want to DIY, start with a mini system before investing in more materials and equipment.

Quick Tip

Choose a plant that already thrives in your climate, as this will lower the electricity cost of maintaining your system and save energy.

Pros and Cons

Between farmed fish and edible fruits and veggies, this type of recirculating agriculture has the potential to increase food production without exploiting water resources, all while recycling the nutrients naturally produced by fish into natural fertilizer.

Especially in arid and semiarid regions, recirculation of water in aquaponics systems can reuse water at 95% to 99% efficiency; the water rarely needs to be changed or dumped since it is continuously recycled. Plus, since it doesn’t use soil, aquaponics doesn’t contribute to topsoil erosion or other negative effects on global soil quality, and there is no need to use chemical fertilizers. Similarly, regular gardening pesticides aren’t used as they could potentially harm the fish, and there’s no chance for any soil-borne disease, either.

Another advantage of aquaponics is that plants can be grown in very small spaces and tend to grow fast thanks to the extra nutritious substances from the fish waste. You can also control the temperature environment easier than in traditional soil farming.

On the flip side, not all crops work well with aquaponics, and there is always the controversy involving fish farms in general to consider. Root vegetables like potatoes and sweet potatoes are some of the most challenging plants to grow aquaponically; the same goes for corn, vine crops, and melons, all of which require either a lot of nutrients or supportive overhead space. And while aquaponics saves water, it can also come with high initial setup costs (depending on the size and complexity of the system) and high electricity consumption due to the water pumps and temperature regulators. Aquaponics is also more technical than traditional farming and other non-soil production systems, so it is more susceptible to unexpected failure and malfunctions (such as when a plant’s roots grow too fast and overcrowd the system).

View Article Sources
  1. Joyce, Alyssa, et al. "Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources." Aquaponics Food Production System, 2019, pp. 19-34., doi:10.1007/978-3-030-15943-6_2