Picking the right water pump trips up a lot of new aquaponics growers. This guide walks through exactly how to size a pump correctly for your own setup, step by step.
Figuring out your target flow rate
Your flow rate target comes from one simple rule: the entire volume of your fish tank should cycle through the system at least once every hour. For example, a DIY IBC-based setup would need a pump rated for roughly 250 gallons per hour at minimum. That rating by itself isn’t the full picture, though – you also have to factor in what’s called the pump’s head height.
How much lift does your pump actually need?
The next thing to work out is how far up you need to push the water to reach your grow system. If the pump is only moving water from a sump into the fish tank, the lift might only be a couple of feet. When you’re planning your layout, try to keep that vertical lift as short as practically possible.
Understanding a pump’s head height
Say you bought a pump rated at 250 gallons per hour for your IBC setup. Does that mean it’ll actually deliver 250 gallons per hour once it’s running in your growbeds? Not quite. That rating is measured at zero feet of head height – meaning it’s the flow you’d get with no vertical lift at all. Once you start pushing water upward, the flow rate drops. Fortunately, most manufacturers publish a chart showing exactly how much the flow rate falls off at different lift heights. This chart is known as a pump curve, and it plots the relationship between flow rate and head height.
How to read a pump curve
Any reputable pump manufacturer or retailer will include a pump curve in the manual or spec sheet. If you can’t find it listed on the product page, search online for the pump’s name plus “user manual” and you’ll usually turn one up. Once you have the curve in front of you, start on the left-hand axis and locate the head height you calculated for your setup, then trace a line across to the right. Then find your minimum required flow rate and trace a line straight up. Wherever those two lines intersect is your pump’s actual working point. In a typical example, that intersection lands right on the line for a 400-gallon-per-hour pump. If your working point falls between two pump lines, always round up to the larger one – never round down, or you won’t hit the recommended one-hour turnover rate for your water. It’s always smart to size up rather than down, since cycling the water more than once an hour beats cycling it less.
In a typical setup – an IBC tote as the fish tank paired with a few growbeds – the tote holds roughly 250 gallons when full. The point where your head-height line and flow-rate line cross tells you the pump size you actually need. In this example, a 250-gallon-per-hour pump wouldn’t actually deliver 250 gallons per hour once head height is factored in, so a 400-gallon-per-hour model is the right choice to hit that real-world minimum.
Recommended pump options for aquaponics
Hydrofarm is a solid, reliable brand that publishes its head-height curve data openly, which makes sizing much easier. Their pump lineup covers a wide range of flow rates:
- 40 GPH (about 150 LPH)
- 160 GPH (about 600 LPH)
- 250 GPH (about 950 LPH)
- 400 GPH (about 1500 LPH)
- 550 GPH (about 2080 LPH)
- 800 GPH (about 3000 LPH)
- 1000 GPH (about 3785 LPH)
Should my pump sit inline or fully submerged?
Most people simply submerge the pump directly in the fish tank or IBC. Just make sure the electrical plug and cord stay well clear of the water when you set it up this way.
How do I connect the pump to PVC pipe?
Check the fitting size on your pump and pick up matching adaptors from a hardware store. The fittings that come with most pumps are designed for flexible hose rather than rigid PVC, so if you’d rather skip the hose entirely, use the pump’s fitting measurements to source the right PVC adaptors.
Conclusion: what size pump does your aquaponics system need?
Sizing your pump correctly really comes down to two factors:
- The head height your pump has to overcome
- The total volume of your fish tank