How To Grow Watercress In Aquaponics

Aquaponics merges two systems with fantastic results for the majority of plants. All you need to do is create the right habitat for your chosen fish and then a separate plant area. The two are connected via a pump allowing the water to circulate.

Watercress is an excellent choice for your aquaponic system. It is relatively easy to grow and will provide a great introduction to the world of aquaponics.

Simply follow this guide and know how to grow watercress in aquaponics in no time; perhaps selling it for a small profit.

Choosing The Fish In Relation To Your Grow Beds

The first thing you need to do is chose the size of your planting area and the size of your fish tank. These two items are actually connected.

As a general guide, you should be looking at 1 fish per every 5 gallons of water. To help you calculate the number of fish you need it may be easier to start with the amount of growing space you have. It is best to have one pound of fish for every square foot of plants.

If your growing area is going to be 2ft by 4ft then you’ll have 8 square feet and need 8 pounds of fish. Once you know which fish you wish to buy you’ll be able to work out how many that is but you must base the number of fish on their adult weight even if you are purchasing baby fish.

For 8 square feet of growing room, you should be looking at between 40 and 80 gallons of water.

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Create Your Tank

Now that you have figured out the size of your system you can make your fish tank. It will need to have the usual ingredients to ensure the fish are happy.

You’ll then need to add a pump that can take the fish water through to your second tank; the growing bed. Of course, the water also needs to flow back to the fish tank.

Ideally, your pump should be capable of moving the entire volume of your fish tank in just 15 minutes.

You’ll also need to add an aerator to the tank to ensure enough oxygen is always present.

Build The Right Growing Media

Watercress is designed to grow in water! This means that you will be best to choose a system such as the floating raft to maximize the growth of your watercress.

This s actually very simple to do at home with materials you probably already have.

  • Start with a standard plastic fruit tray; the type that has a grid structure on the bottom and sides. You’ll need to remove any labels and clean the tray thoroughly; you don’t want to introduce the wrong bacteria to your system.
  • Next, you’ll need to find or cut 2 pieces of polystyrene. They need to be roughly the same length as the tray and approximately 1 inch thick.
  • Tie one piece of polystyrene to each side of the tray with new cable ties.
  • Now place the tray into your growing tank. The water should be several inches deep but you want it just to be lapping at the bottom of the tray; enough so the plants can access the water bit not so that they are drowning in it. You can adjust the amount of polystyrene to get the float level right.

Now your system is ready but you need to complete several more tasks before you can start growing your watercress.

Filling The Tank

You can just add water from the tap to your fish tank. But, if you do this you’ll need to turn on your pump and aerator. These should be left to run for approximately 3 days; this will ensure any chemicals in the tap water have gone.

You can add chlorine removing products but if you have the time it is best to let the process happen naturally.

Add Bacteria

Add some ammonia to your fish tank. This will encourage the growth of the bacteria which will convert the fish waste into nitrates for the plants. It is vital you do this before you introduce the fish and the plants.

The process will take approximately 2 weeks which can be frustrating but it will ensure the right environment is created for your fish and watercress.

As a rough guide, you’ll need to put one cup of ammonia in and add a capful each day for the two weeks.

It is advisable to test ammonia and nitrate levels every day. When there are very few or none of these you should be ready to bring in your fish.

Dropping The Fish In

Once the bacteria are ready you can add the fish. Don’t forget that they need to be given time to acclimatize to the water. Keep them in a bag of water for several hours before allowing them to swim into the main tank.

You can always start with a couple and then add the others once you’re confident that they are happy and comfortable.

Add Your Watercress to Aquaponics

how to grow watercress in aquaponicsThe easiest way to get started is to purchase some watercress seeds. Then line the bottom of your floating raft with cotton wool or hemp fibers; this is your growing media. Sprinkle your watercress seeds across the top of the growing media in the same way you would if planting in soil.

Gently place the tray into the water and wait for them to grow.

It is possible to grow watercress with cuttings if you prefer; just sprinkle them across the tray.

In future years you may wish to retain the seeds from the watercress you have grown; allowing you to produce more for nearly zero cost. Get watercress seeds here.

Now sit back, relax and watch how quickly your watercress grows. This is one of the best plants to grow in an aquaponics system and should provide you with a bumper yield. Do you want to grow more plants in your aquaponics setup? Read our guides on the best plants for aquaponics.

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