How To Build An Aquaponics System To Raise Fish For Food

By Nick Oetken
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How To Build An Aquaponics System To Raise Fish For Food

Nick Oetken
 
Aquaponics plants growing in metal pipes with circulating water from a fish pond, permaculture farm project.
Aquaponics plants growing in metal pipes with circulating water from a fish pond, permaculture farm project.
 
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Aquaponics is defined as merging hydroponics, or the growing of plants in water, with aquaculture, or raising marine life.

To put it in simpler terms, aquaponics is the process of where you raise fish, and use their waste to nourish your vegetables. The result is that you create a completely self-sustainable source of food that you can live off, as an alternative or an addition to stockpiling food.

It’s an efficient closed-system form of agriculture that can be cheap to build and run (with a little ingenuity), and has the potential to yield bumper crops.

HOW DOES AN AQUAPONICS SYSTEM WORK?

After the plants have filtered the water it is cycled back to the tank.
After the plants have filtered the water it is cycled back to the tank.

Pretty much any container of suitable material, be it PVC pipes or a bathtub, will do for planting your crops. The grow bed needs to be filled with gravel or clay beads. No soil is used in aquaponics.

The system works by pumping the water mixed with waste from the fish tank into the grow bed, either directly or via a flood/storage tank. The nutrient-rich “sewage” water feeds the plants, and the plant roots filter the water before it is cycled back to the tank. The returning water will be clear and of a favorable pH for your fish.

Practically any kind of vegetable can be used in an aquaponics system — lettuce, spinach, and kale are among the most popular — while the best fish to raise with this method are catfish, bass, and trout. Once your system gets up and running, you will have a nearly endless supply of fresh fish and produce for the dinner table.

ASSEMBLING YOUR EQUIPMENT FOR THE AQUAPONICS SYSTEM

Next, let’s discuss how you can build an aquaponics system. It is highly recommended that you build your aquaponics system inside a greenhouse, rather than outside, so that it can be kept up and running throughout the year.

• Tank for the Fish

Healthy fish need plenty of room to swim and grow.
Healthy fish need plenty of room to swim and grow.

The first thing that your aquaponics system needs is a tank, specifically a tank that is capable of supporting at least one fish per 10 gallons of water. The reason for allowing so much space is because fish need space to swim and live comfortably.

Therefore, if you plan on raising 25 fish, you should have a tank or bin that is at least 250 gallons. If you only want to start with five fish, then a 50 to 60 gallon container will work.

Make sure that the tank, bin, barrel, or whatever it is you choose to hold your fish is completely clean and has never come into contact with toxic materials in the past that could have a bad impact on the fish.

• Container for the Vegetables

Lettuce from a hydroponics system.
Lettuce from a hydroponics system.

Since your vegetables are growing in a soilless medium, they will need a container that is water resistant to grow in. Keep in mind that the container for the vegetables is separate from the fish tank.

You have a number of options before you, such as building a wooden box yourself that you would line with pond liner, or utilizing any sturdy, water resistant container, but again choose something that has never been used for holding anything toxic.

You will then need to fill up with bed with a growing medium, fine gravel being the best choice since it works well and is cheap. Very small river stones are another option provided they are well scrubbed before use.

Special bacteria that convert ammonia to nitrates can be purchased to add to the grow bed as an additional biofilter. This makes plant uptake of nitrogen compounds more efficient, and returns less to the fish tank.

• Hardware Equipment

A solar powered pump works best to make your aquaponics system truly self-sufficient.
A solar powered pump works best to make your aquaponics system truly self-sufficient.

The reason aquaponics works is because the plants will filter the waste out of the fish tank and allow the fish to live in clean water, while the nutrients provided by the fish waste are used as a fertilizer for the plants.

Therefore, you need to install a pump that will circulate the water between the plant beds and the fish tank, and an aerator to provide oxygen.

A solar powered pump (at least as a backup) works best to make your aquaponics system truly self-sufficient. It’s worth considering adding aquatic plants as a power-out back-up oxygen provider. These will also provide shade on hot days.

You will need to install PVC pipes that connect the fish tank to the grow bed. These pipes should be at least one foot apart from one another and at least a quarter inch in diameter.

• BUILDING THE AQUAPONICS SYSTEM

The possibilities for planting out a grow bed are fairly endless.
The possibilities for planting out a grow bed are fairly endless.

The space where you set up your aquaponics system in needs to be flat, warm, and receive plenty of sunlight. This is why we recommend a greenhouse, because it provides your aquaponics system with all three of these things. Furthermore it allows you to keep using your system during the winter time.

If you choose to set up your aquaponics system outside anyway, assemble it in the early spring right when the temperature of the water in the tank will be around 70 degrees Fahrenheit.

Set up the plant bed first and get your plants growing before you add the fish; this is because without the plants, the water will not be filtered and the fish will be trapped in a tank filled with their own filth.

Be sure to keep a close eye on your aquaponics system to make sure that it is running properly and to fix anything that isn’t. The most important components of the system that need to be working well all the time are the aerator, which delivers oxygen to the fish, and the pumps, which transfer the water between the plant beds.

You can always tell if the pumps are working by how murky the water in the fish tank is; if it’s excessively murky, then that’s probably a sign that either the plants are not doing their job, or more likely that the water is not transferring between the two correctly.

Suitable fish to raise in an aquaponics tank include tilapia, trout, bluegill, and even prawns.
Suitable fish to raise in an aquaponics tank include tilapia, trout, bluegill, and even prawns.

Finally, you have to feed your fish! Fish will eat three times a day and will consume all that they can within fifteen to twenty minutes.

You can either feed the fish by hand yourself, or better yet you can install an automatic feeder over their tank that will feed the fish a specified amount of food at key points during the day.

Do not overfeed the fish because doing so will only worsen the water conditions and make filtration by the plants more difficult. Start off small and then gradually add more food as the weeks go on until you are giving them the right amount.

 
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