The Prepper Journal

Using Fish to Create Organic Fertilizer

In this article we’re going to discuss how you can grow plants using fish in an aquaponics system.

Aquaponics is the combination of hydroponics (a method of growing food without soil) and aquaculture (fish farming).

Using Fish to Create Organic Fertilizer - The Prepper Journal

The two things work in unison with each other, the fish provide waste which creates a fertilizer for the plants, and the plants clean the water which cycles back to the fish.

This method is perfect for preppers who don’t want to rely on shops or farms and want to become self-sufficient and find a productive and easy way to grow your own food.

This system requires very little intervention once it is set up and running, and pretty much runs itself. Not only will in provide you with an abundance of vegetables, but you can also breed and harvest the fish so you have a never ending supply of fish and plant based foods.

The Process Behind Aquaponics

So how does aquaponics actually work?

The main job for you as a prepper is to keep the fish fed. The rest of the system really does look after itself.

Once they’ve been fed (ideally with organic fish food) the fish will eat the food and produce waste. Some of their waste will be ammonia (urine) and the rest will be fecal matter.

The essential bacteria which will have built up in the fish tank will help to convert the ammonia into nitrites, and then into nitrates.

These nitrates are then passed onto the plants as food, so not only do they thrive, but the fish tank doesn’t need to have water changes carried out as a regular fish tank would. (The main reason for water changes is to remove the build-up of nitrates).

The bacteria in the system play just as big a part as the fish and the plants, without it, the cycle wouldn’t work.

What does an Aquaponics System look like?

Most systems are built in vertically, one on top of the other. The fish tank sits underneath, and the tray or growing bed which the plants grow in sits on top.

There will be a gap between the two which allows you access to the fish at all times.

Some aquaponics systems are set up with the fish and plant components sitting side by side.

What Do you Need to Set Up An Aquaponics System?


You’ll need a tank or some type of container to keep your fish in, the size of your system is driven by how much food you want to grow which is determine by the type and size of fish tank you use. As a good indication, you can achieve 1 – 2 square feet of growth area for every 10 gallons of water in your fish tank.

You might want to set up a small indoor system to grow herbs; in this case you can use something as small as a 10 gallon fish tank. If you want a larger outdoor system, you can use a much larger tank, there is no limit. You can either use a glass or acrylic tank; some people choose to use a plastic tub or barrel.

You’ll need gravel for the bottom of the tank, this will act as a bed for the bacteria to grow on which is vital to break down ammonia and nitrites.

You’ll also need a water pump and around 3 feet of tubing to connect the tank to the grow bed where you’ll be growing the plants.

You should also have an air pump to help oxygenate the water, and a pH kit to test the water every couple of weeks.

For the grow bed, you can use a wooden crate, a plastic tub or a plexi-glass container. The depth needs to be at least 3 foot. You’ll need a growing medium, because aquaponics systems do not use soil. Most people choose to use clay pebbles, pea gravel or perlite.

If you choose to house tropical fish in the tank, you’ll also need an aquarium heater, although most people choose fish which thrive in cold water tanks.


There are a whole range of fish which you can use in an aquaponics system. The species you’ll choose will depend on whether or not you are growing the fish to harvest.

I’d imagine, being a prepper and wanting to be as self-sufficient as non-wasteful as possible, that you’ll most likely want to choose species which you can also grow to eat.

These include larger species such as:

  • Tilapia; these are the most common and popular fish used in aquaponics. They are quick growing, breed well, taste good, and can be fed using the food you grow.
  • Silver Perch; they are omnivores, but a large percentage of their diet is plant based so you’ll be able to grow the vast majority of their food.
  • Barramundi; these fish require warmer water so you’ll probably need a heater depending on where you live. You’ll also need a lid as they’re jumpers.
  • Trout; these fish are fast growing, but they like to jump so you’ll need a lid on the tank

If you are vegetarian or just don’t want to eat the fish in the system, some people choose to have ornamental fish. A few examples of these are:

  • Goldfish; they come in a wide variety of colors and shapes and can tolerate a wide variety of water conditions.
  • Any smaller species such as guppies, mollies and tetras.


There a lots of different plant you can grow in an aquaponics system, again, this will depend on the size of your setup and what you want to achieve from it.

If you’re having a small indoor system you’ll probably only have space to grow small plants such as basil, mint and watercress.

If you set up a larger outdoor system, the options are endless. In a new system these are some of the foods you can grow:

  • Lettuce
  • Tomatoes
  • Peppers
  • Cucumbers
  • Broccoli
  • Cauliflower
  • Cabbage
  • Squash
  • Peas
  • Rocket
  • Kale
  • Spinach
  • Swiss Chard

Once your system is more established, you can grow other crops such as:

  • Sweetcorn
  • Carrots
  • Radishes
  • Onions
  • Edible flowers
  • Blueberries

It’s likely that you’ll probably have a good store of food for when SHTF, but have you thought about a more long term solution to growing your own food without access to ongoing supplies such as soil and fertilizers?

An aquaponics system will provide you with a self-sustaining system which will provide you with an abundance of food.

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