Chapter Five: Water Systems for Plants

There are two ways to cycle water through your aquaponics system:

• Flood and Drain (also referred to as ebb-and-flow)
• Continuous Flow

Here is how each one works:

Flood and Drain

• Through the use of a water pump located in the fish tank, or container, the fish water is pushed up and into the media bed.
• The fish water fills the media bed until it reaches the desired flood level, determined by the height set in the bell siphon. 
• When the bell siphon “trips,” the fish water drains back into the reservoir.
• When the bell siphon is empty, fish water begins to flow back into the media bed with the help of a water pump.
• This usually takes 15 minutes.
• A timer is set to run for 15 minutes on, then 45 minutes off.
• If your bell siphon runs for 15 minutes every hour and you have a 200-gallon tank, you need a water pump that circulates 800 gallons of water per hour.
• You will need to determine how far against gravity, you need to move the water, otherwise known as "the lift.”
• Use the sliding scale listed on the water pump package to see how much power you need.

Continuous Flow

While Flood and Drain is the preferred form of cycling water, Continuous Flow is another option. This type of water flow is the same as the flood and drain. However, the timer is removed, so the water can continuously cycle through the system. Two of the downsides of this type of cycling are that the pump is in the fish tank, and the plant's roots can become waterlogged as areas of the grow bed can become stagnant.

Determining the Right Water Pump

Water pumps come in all sizes to meet your specific aquaponic garden's needs. When deciding which water pump is best for your system, the first thing you will want to determine is the Gallons Per Hour (GPH).  Nearly every pump has information regarding the GPH. Typically, the water pump should cycle the water through your system one time every hour, so the pump you choose should meet this requirement.

So, if you have 200 gallons of water in your system, you will need a pump that pushes 200 gallons per hour, meaning 200 GPH.

To make sure your pump meets your water cycle needs, you will also need to measure the head height of your fish tank. The head height is the amount of space between your fish tank, and your grow bed. The reason for this is that the larger the headroom, the more energy is required to pump water. Obviously, in setups, where the fish tank and the grow bed are side-by-side, or at the same level or share the same container, have no headroom.

Once the calculation between the GPH and head height is figured out, then the right pump size can be determined. Water pump packages often come with a chart that combines these two for you. By combining the GPH and head height, you will be able to find the best pump to meet your water cycling needs.

Types of Water

Water is the main artery of every aquaponic system. Water takes up most of the space and must be monitored to make sure it is balanced and healthy for your fish tank and grow bed.

Water has many parts, and each one needs to be understood. In aquaponics, when it comes to water, the following must become very familiar to you:

• Alkalinity should be at least 100 ppm
• Ammonia should be 0.25 ppm or less
• Dissolved Oxygen should be maintained at five ppm or higher
• pH requirement is between 6.8 and 7.2
• Water Temperature should be 65° to 85°F for warm, 55° to 65°F for cold

Other Water Reminders:

• Add water to grow beds rather than the fish tank.
• Cycle water to remove chlorine and chloramine
• Test the water daily in a new system
• Record all water readings in a notebook.
• City water should be checked for chlorine, nitrites, nitrates, bacteria.
• Never remove more than 1/3 total water volume at once. Instead, do 1/6th in the morning and 1/6th at night.
• Rainwater might contain dangerous substances.

Ways to Resolve Water Issues:

• Purchase a hose device
• Aeration, aeration, aeration
• Run system with just water in it for a couple of days to eliminate chlorine

Chapter Five Checklist

• There are two ways to cycle water through your system: Flood and Drain, Continuous Flow.
• The right pump is determined by the Gallons Per Hour (GPH)
• The head height between the fish tank and grow must also be considered.
• Add water to grow beds rather than the fish tank.
• Test the water daily in a new system
• Record findings in a notebook
• Never remove more than 1/3 of tank water at a time.
• Rainwater can be dangerous.
• Aeration is a great way to resolve some water issues.