Choosing the correct pump for your aquaponics systems is as important or more important than choosing the right fish, bed material, tank size and grow bed size.
Without the right pump your fish will die, your plants will die and your fun will come to an end very quickly.
Some folks simply head to the hardware store, pool supply store or pond supply store and purchase the first pump they find or the first pump that the retailer recommends. Please do not buy your aquaponics pump this way.
Some retailers are very informed when it comes to growing fish and plants together, MOST ARE NOT!
If your pump supplier does not ask simple questions like:
- How much water is in your system?
- How high does the pump have to raise the water?
- Are you using a siphon or timer system?
I am kidding…sort of. The fact is that so many homesteaders get the wrong pump the first time. Sometimes this is a minor inconvenience and sometimes it is a total disaster leaving your fish dead, you frustrated and your family members wondering why you can’t make this work.
In an off grid aquaponics system your pump must be considered very, very carefully. Having a cheap pump that is horribly inefficient will result in disaster the first time your off grid electric system cannot supply enough power.
The absolute minimum information required when purchasing your pump for your aquaponics system is the amount of water contained in your whole system.
Aquaponics Pump Flow Rate
As a general rule, your pump should circulate all of the water in your aquaponic system at least every two hours.
Make sure the pump you choose will meet this minimum standard of cycling half your system’s water every hour.
- You have a 100 gallons of water in your system.
- You will need a pump that can move at least 50 gallons per hour (.83 gallons per minute).
Keep in mind the pump’s flow rate will change depending on the head (difference between water level of grow beds and fish tank).
The flow rate of your aquaponics pump will either be measured in:
gallons per hour (gph), gallons per minute (gpm), liters per hour (lph) or liters per minute (lpm).
- 1 gallon per hour = .0167 gallons per minute / 4 liters per hour / .0667 liters per minute
- 1 gallon per minute = 60 gallons per hour / 240 liters per hour / 4 liters per minute
- 1 liter per hour = .250 gallons per hour / .004175 gallons per minute / .0167 liters per minute
- 1 liter per minute = 15 gallons per hour / .250 gallons per minute / 60 liters per hour
The flow rate will change depending on the head or the height the water must be pumped. As the head increases the flow rate of your pump will decrease. Be sure to keep this in mind when deciding on your pump.
Head Pressure in Your Aquaponics System
Head or head pressure is the difference in water level between your fish tank and your grow beds. If the grow bed and fish tank are level you would have no head. The more head in your system, the more electricity will be required to move a specific amount of water. It takes 1 pound per square inch (PSI) to move water up 2.2 feet. The more head, the more pressure required to lift the water.
If you are trying to make your system as efficient as possible, try to keep your head to a minimum.
Some pumps have no trouble overcoming many feet of head while the more efficient units will likely pump less water at even 5 or ten feet of head pressure. Circulating pumps (like those used in heating systems) are a good example of this. If you have only a few feet of head in your system, it is likely a circulating pump will be the best pump for your off grid aquaponics system. Most circulation pumps are made to operate continuously and consume less electricity than most pressure pumps.
The pump specs listed to the right would be suitable for a very small, low head aquaponic setup. The SID3.5PV is a 3 1/2 watt solar pump, the SID5PV is a 5 watt solar pump and the SID10 models are all 10 watt pumps. Learn all about the SID pumps here.
If we had 3 feet of head and wanted to use a model of this pump (SID10B12), it would pump about 1.5 gallons per minute or 90 gallons per hour. Since we want to move all of our water every two hours we could use this pump for an aquaponic system containing about 180 gallons. That is not a super small system by any means. It is amazing that a pump using only 10 watts can perform so well.
Energy Efficiency of Your Pump for Aquaponics
All pumps are different. One pump may take 100 watts to move 5 gallons per minute up 10 feet while another might only use 30 watts.The difference is how much heat the pump produces. The 100 watt unit will make 70 more watts of heat than the 30 watt pump forcing you to purchase more solar modules, purchase a larger wind turbine or using the generator more. If you go to the average big box store for your pump, you will likely get a very inefficient pump. Big box stores do not care about efficiency, they care about profits.
And good luck trying to find the efficiency for the pump you want to buy. It will not be listed anywhere on the spec sheet.
If you are lucky, you might be able to get an accurate wattage rating on the box or specification sheet for your new pump. However, most of the wattages listed on the box/spec sheet are very inaccurate. The only way to accurately measure power consumption is by using a digital multimeter or Kill a Watt Meter.
The only detail you really need to care about is:
“How much electricity will my pump consume per day in my system?”
Daily power usage equals wattage of pump multiplied by 24 hours.
watt hours = wattage of pump x hours of operation
As you are living off the grid every watt hour counts. Taking a little extra time and care right now will save you a lot of headache later. Your system must operate flawlessly everyday or you will lose plants and/or fish.
You do not want to get a call on a sunless day from your wife/husband telling you the power is out and the fish are floating.
AC or DC?
How much water in your system?
Are you using a siphon system or timer system for flood and drain?
Considerations when trying to make your pumping system as efficient as possible:
- The higher the flow rate (amount of water being pumped), the more electricity will be required.
- The higher the water must be pumped (the higher the head), the higher the electricity consumption.
- A timer system will use less electricity than a siphon system as the pump will operate less.