Hydroponics With Fish (An Intro To Aquaponics)

Hydroponics with fish – sure it may sound a little peculiar, but it’s actually both a fascinating and very practical means of cultivation.

What’s more, aquaponics will satisfy hobbyists out there who are interested in both growing plants and raising fish.

Perhaps most importantly though is the fact that this system is an environmentally friendly agricultural practice.

What more could you ask for?

If the above points have piqued your interest, then you’re sure to find plenty of value in the information to come.

This overview of aquaponics will address how the system works, its advantages and disadvantages, what fish you can use, and the types of aquaponic systems out there.

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What Is Hydroponics With Fish?

Aquaponic System with Koi Fish
Aquaponic System With Koi Fish

Aquaponics is a food production system that combines hydroponics (growing plants without the use of soil) and aquaculture (the cultivation of aquatic organisms in controlled aquatic environments). It is therefore easy to see why some may refer to it as hydroponics with fish.

But why would you want/need to use such a system?

In a hydroponic system, you need to replace your aqueous solution every 2/3 weeks. This prevents the over-accumulation of fungi, nutrients, and bacteria.

The same goes for an aquaculture system. Toxic nutrient accumulation occurs from fish, fish waste, and fish food. This results in you having to continuously reintroduce a clean water supply to your setup.

Aquaponics solves the above issues through a symbiotic relationship between fish and plants.

In this system, microbes in the water convert ammonia from the fish waste to nitrates which the plants then take up and use to grow. In turn, the plants act as biofilters, providing purified water that returns back to the fish tank.

This continuous, mutually beneficial cycle reduces effort and results in you having healthy fish, happy plants, and minimal water wastage.


How Does An Aquaponic System Work?

A variety of aquaponic systems exist. They can vary in size, complexity, and setup.

But every aquaponic system has three key elements:

  • Fish
  • Plants
  • Bacteria
Diagram illustrating Aquaponic Process
Aquaponic System Diagram
Credit to: Jilian Helvey
Source: aquaponichowto.com

Fish

Fish are responsible for feeding your plants and as such, they play a vital role in your aquaponic system. The waste that they produce acts as a natural fertilizer.

They can be of an ornamental or food variety. Either way, selecting the appropriate fish is critical to the success of your system.

Continue reading to find out which fish are best suited to aquaponic systems.

Plants

As previously mentioned, plants act as a biofilter. They detoxify the water by absorbing the nitrates and other impurities, allowing it to recirculate back to the fish. In doing so, they remove the need to continuously replace water, lowering your water usage.

Bacteria

The unsung hero of the aquaponic system.

The bacteria present in this system transform fish waste into nutrients for the plants through nitrification. Nitrification takes place by means of the nitrogen cycle.

The Nitrogen Cycle

A diagram of the Nitrogen Cycle
Credit to: Agriculture Academy

This cycle in Aquaponics follows 4 specific steps:

1. Ammonification

Ammonia is a waste product from the respiratory cycle of the fish as well as decomposing fish food and fish waste. While the presence of ammonia is essential, when it accumulates in high concentrations it becomes toxic to the fish.

2. Nitrification

Next, we have a naturally occurring, nitrifying bacteria called Nitrosomonas. These exist on every dark wet surface in the aquaponic system. Their function is to convert ammonia into nitrite.

3. Nitrification (Again)

Nitrite, however, is even more toxic to fish than ammonia. This is where Nitrobacter plays a role. Nitrobacter converts the nitrites to nitrates.

4. Assimilation

These nitrates are a great source of nutrients for the plants.

In summary: Ammonia is converted by naturally occurring Nitrosomonas into nitrites. Nitrites are then converted by nitrobacteria into nitrates. These nitrates provide nutrients for the plants.

As you can see, the nitrogen cycle and its bacteria play a critical role in converting toxic waste products into viable nutrients that the plants can use.


Basic Components Of An Aquaponic System

If the concept of hydroponics with fish excites you, then you’ll want to know more about the equipment involved in the process.

Let’s have a closer look at some of the basic components that make up an aquaponic system.

  • Fish Tank
  • Grow Beds
  • Grow Media
  • Biofilters
  • Water Pumps
  • Electricity
  • Water Heaters/Coolers

Fish Tank

This is where your fish will be living.

Criteria for a fish tank:

  • Must sized approprietly for your fish species.
  • Try to choose a round tank. Rectangular tanks are prone to issues – they allow solid waste to collect and rot in corners.
  • Invest in a tank with great build quality – must be durable and waterproof.
  • Made out of food-grade material.
  • Select a user-friendly tank that has a configuration allowing for easy solid waste removal.
  • The fish tank must be on a solid surface, prop it up if necessary.
Recommended materials: Any appropriately sized structure that you can line with an EPDM pond liner will be suitable as a fish tank. Other options include recycled bathtubs, stock tanks, IBC tanks, and recycled barrels(DIY).

Grow Beds

This is where your plants grow. The size of your fish tank determines the size of your grow beds. The bigger the grow bed and the more plants there are, the more fish waste required

Criteria for grow beds:

  • In general the recommended grow bed to fish tank ratio is approximately 1:1.
  • Made out of food-grade material.
  • Strong enough to hold growing media and water.
  • Able to withstand weather conditions.
Recommended materials: Grow beds can be made from the same materials as a fish tank.

Grow Media

Grow media is the substance that provides structural support to the plants while holding water and nutrients for the plants to grow. Additionally, it acts as a biofilter.

Criteria for grow media:

  • Lightweight
  • Mid-sized
  • Porous
  • Neutral pH
Recommended materials: crushed rock, hydroponic clay, aquarium gravel, or those made of synthetic materials.

Biofilters

While your media beds can serve the same purpose as a biofilter, you may wish to include a separate system as part of your design if you have the space to do so

Water Pumps And Piping

These circulate water and oxygen throughout your aquaponic system.

Electricity

Any pumps or lights that you add to your setup require electricity, so you’ll need to link up to your electrical grid. Alternatively, you can make use of your solar panels to generate the required energy.

If you don’t have a solar system at home but are interested in learning about how to set one up, check out this article.

Water Heaters/Coolers

If you live in very hot or cold regions, then you may also want to invest in water heaters or coolers.


Types of Aquaponic Systems

The great thing about aquaponic growing is that you can be flexible in your approach. The system lends itself to a number of variations.

Let’s take a look at the 4 hydroponic growing methods used in aquaponics.

  • Deep Water Culture (DWC)
  • Flood And Drain (a.k.a. Ebb And Flow)
  • Nutrient Film Technique (NFT)
  • Drip Irrigation

Deep Water Culture (DWC)

Lettuce growing on a DWC raft
Lettuce Growing On A DWC System Raft

To learn more about the DWC method, check out our comprehensive article –
DWC Hydroponics (A Beginners Guide To Deep Water Culture)

Flood And Drain (a.k.a. Ebb And Flow)

Mint Growing In A Flood & Drain System
Credit To: AgeHans on Reddit

This system irrigated the plants by filling the hydroponic basin with nutrient-rich water followed by a period of draining which draws air into the root zone.

Intermittent exposure to water and air introduces oxygen to the roots, creating an optimal environment for them to flourish.

Additionally, coarse substrates such as expanded clay or perlite are used for root stability, drainage, and biofiltration.

Nutrient Film Technique (NFT)

Nutrient Film Technique Hydroponic System
NFT System
Credit to: Chakkapong Benjasuwan 

The NFT method uses narrow channels, such as PVC pipes, to transport nutrient-rich water.

Holes are drilled into the pipes and the plants are placed into them. In this position, their roots can hang freely and make contact with the stream of water.

This system is suited to plants that require little in the way of support, e.g. herbs and strawberries

Drip Irrigation

Water flowing into the substrate from a drip irrigation system
Water Flowing Into The Substrate From A Drip Irrigation System

This system uses growing media that provides the roots with a constant supply of water and air.

Bucket (Dutch or Bato) culture is generally used for large fruiting crops like peppers, cucumbers, and tomatoes.

Bucket culture combines both flood and drain, and NFT. This creates a modular, mobile growing method.

Substrates involved in bucket culture systems include but are not limited to: rockwool, perlite, expanded clay.


What Fish Are Best For Aquaponics?

It’s critical that you understand the purpose of and plan for the fish in your system, after all, this is hydroponics with fish.

Here are some criteria that you need to consider before purchasing fish:

  • Ornamental Or Edible
  • Temperature
  • Fish availability & Aquaculture Law
  • Maintenence Requirements
  • Size & Space Requirements
  • Filtration
  • Breeding Habits
  • Fish Diet

Ornamental Or Edible

Are you looking to harvest your fish for food or have them purely for ornamental purposes?

Species like Tilapia and Carp are commonly used for food, but they can be trickier to maintain, whereas ornamental species such as Koi and Goldfish are more forgiving and resistant to conditions and diseases.

Temperature

Fish require specific, steady temperatures in order to thrive, but different fish have different temperature requirements. Consider the environmental temperature as well as the temperature requirements of your fish before you go about purchasing them.

Fish Availability & Aquaculture Law

Consider the availability of fish in your location as some species are only found in certain areas.

Also, be sure to read up on any fish farming laws that are applicable to your area. Not all fish are legal to be purchased and grown in some locations.

Maintenence Requirements

How much maintenance are you willing to put up with? After all, your plants aren’t the only ones that need TLC, and some fish require more maintenance than others.

If you’re a beginner or someone wanting a low maintenance setup then a hardy species such as Koi or Tilapia will be right for you

Size & Space Requirments

Space is important to your fish. Be sure to research the adult size of the fish that you are looking to raise and plan the size of your tank accordingly.

Filtration

Your filtration capacity will determine the amount of fish that you can have in your setup. Get this wrong and you will deprive your water of much-needed oxygen – your fish and plants will suffer as a result.

Breeding

You will need to learn and plan for the breeding habits of the species that you have chosen. Some breed more easily in captivity than others, and as such your setup may require additional space.

Fish Diet

The types of fish that you choose will determine the food that you have to buy. Be mindful of the fish food availability in your area as well as the projected cost of buying this food – the last thing you want to do is exceed your budget.

This also brings into question the species of fish that can be housed with one another. Some are carnivores while others are herbivores or omnivores.

Make sure that one species of fish you have chosen won’t eat or fight with another.

With all of that in mind, here is a list of 10 fish suited to aquaponic growing:

  • Tilapia
  • Trout
  • Catfish
  • Carp
  • Koi
  • Goldfish
  • Bluegill
  • Salmon
  • Bass
  • Barramundi
  • Yellow Perch

What are the Pros and Cons Of An Aquaponic System?

Every system comes with its advantages and disadvantages – aquaponic systems are no different.

Here are some of the pros and cons associated with aquaponic growing:

Pros

  • Minimal water wastage due to its cyclical nature.
  • All natural fertilizer source from fish waste.
  • Produce is herbicide and pesticide free.
  • Intergrated system is sustainable and eco-friendly.
  • Farm fish and cultivate plants at the same time.

Cons

  • Aquaponic setups generally take up a lot more space than other setups – not as modular.
  • They can be power hungry, particularly during winter. Water pumps, heaters, coolers and lighting all add up to increased electrical consumption.
  • The water, fish and mechanical parts all require maintenance. This can be time consuming.
  • The initial investment can be rather expensive.

Final Thoughts

We hope that you’ve found this introductory article on aquaponics both enjoyable and informative.

If what you’ve read excites you, use this foundational knowledge as part of your journey into aquaponic growing.

And as always, please feel free to ask any further questions in the comment section below!

Robert Wortrich

Robert is a content creator and editor. His passion for researching and the environment led him to joining the Climatebiz team. When he isn’t busy writing articles or learning more about everything Green Technology-related, you’ll find him spending time with friends or hiking one of the many wonderful trails that his home – Cape Town – has to offer.

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  1. I bought CHUWPI AquaOrganic Aquaponics Fish Feed as we have an all organic aquaponics set-up and we wanted to keep the fish organic as well. We bought fingerling tilapia, and at first I thought the size of the food would be too big for them to swallow, but the pellets can become soft enough for my fish tank pets to pick at them. This product comes with an organic guarantee and explanation in detail about what’s in it. Besides that, it is also highly recognized for being purely organic fish food that does not contain any fish meal or GMO ingredients.

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