Every system is different. Maybe you are planning to run a large aquaponics system with a large DWC beds, or maybe you plan on running a small hydroponic setup using NFT. No matter the system, choosing the right pump is important, and choosing the wrong size can cause problems long term.
Use the calculator below to find the right pump for your system. Below the calculator I’ve included a description for each field and cons for using the wrong pump size.
Water pump calculator
Calculator help
- System type: Aquaponics and hydroponics systems have different flow requirements, but they use the same type of pump in most cases: high flow and low pressure. PS: You might need a pump with higher pressure and less flow for aeroponics misting systems, or for systems requiring higher head, this type of pump is not included here yet. If you don’t require high pressure, select hydroponics.
- Grow system type: Some grow system types require a larger pump to overcome the system’s pressure resistance. This is added to include a reduction factor in flow. Adding the types of grow systems you have takes this into account when calculating pump requirements.
- System volume: This should include all the water in the system, including the fish tank, sump, and any grow beds(especially DWC) holding water. For aquaponics, as long as you have a sump and no DWC beds, it should be sufficient to include the fish tank and sump volume. Or just the sump in the case of hydroponics.
- Head height: The circulation pumps we use for most aquaponics and hydroponics do not perform well with great heights(head pressure). The big problem with estimating pump size and implementing this is that smaller pumps have less head pressure than larger pumps; and it’s not a linear scale. So we add 30% pump capacity for each meter of height. If you have a smaller hydroponics system (<200L) you might want to go bigger than estimated by this calculator. But we have to include this because there is always some height to overcome in any system, and not including it would end up with a far too low estimate. PS: The value is not the total system height, but from the lowest water height(i.e., sump) to the highest(pumped) water height
- Desired turnover rate: In most systems once per hour seems to be the ideal flow. In aquaponics the fishtank should be circulated 1-2 times each hour depending on the fish type. Hydroponics might need half that depending on the grow system.
- Pump type: All pumps give off heat as they run; adding an internal pump will better cool the pump but also give off that heat to your system; they tend not to be of the same quality as external pumps but are also much cheaper. They can be harder to replace depending on your system design, use a flexible hose to easily take the pump out of the system to replace it. An external pump can be better for larger systems that require better flow and pressure, they are mostly easier to replace as they aren’t submerged, they also don’t give off that much heat to the water as the internal pump, but they do give of the heat to their surroundings. Additionally: there is the hobby style pump(aquarium and pond pumps) and there is the industrial type pump, I’m betting you can guess which cost the most and last the longest, the industrial type is also in most cases more energy efficient when we reach several hundred cubic meters each hour, but for a small hobby system this is a waste and completely overkill.
Use valves
Including valves on all outlets from your pump to your different system parts is important as it gives you the option to limit(or stop for maintenance) water flow to certain parts of your system, this way you can always reach your flow goal to each part of the system.
If you have an external pump, you should also include a valve on the inlet side of your pump; this way, you can quickly stop the water backflowing (i.e. from the fish tank) while replacing the pump without dismantling any more of your system than you need.
Why choosing a too-small pump could cause problems:
- Inadequate Water Flow: A small pump may not have the capacity to circulate water fast enough through the system. This can lead to areas of stagnant water, causing poor distribution of nutrients and resulting in nutrient deficiencies in plants. In aquaponics, this will also result in too little flow through your fish tank.
- Oxygen Deficiency: In aquaponics, a too-small pump can fail to provide sufficient oxygenation to the fish and plant roots. Water movement is crucial for gas exchange, and if the water isn’t cycled often enough, oxygen levels can drop, leading to stressed fish and poorly growing plants. I always recommend including an air pump and airstones for aquaponics, even if you have enough water flow.
- Unbalanced Nutrient Distribution: With insufficient flow, nutrients may not reach all areas of the grow bed evenly. This can cause uneven plant growth and stunted development in certain parts of the system, particularly for larger or multi-tiered setups.
- Clogging Issues: Smaller pumps may be more prone to clogging from fish waste or debris in aquaponic systems, or from mineral buildup in hydroponic systems. They often have smaller inlets or weaker mechanisms, leading to frequent maintenance issues and interruptions.
- Inability to Overcome Head Height: If the head height is higher than what the small pump is rated for, the pump won’t be able to move water effectively, if at all. This can leave parts of the system without water altogether, putting plants at significant risk of dying. For aquaponics, this might also cause your fishtank to be without circulation.
Why choosing a too-large pump could cause problems:
- High Energy Consumption: A too powerful pump consumes much more electricity than needed, resulting in higher energy costs. Your pump should run continuously for the best lifetime, so the running costs can quickly escalate and reducing the cost efficiency of your system.
- Risk of Root Damage: In both hydroponics and aquaponics, a pump that produces excessive water flow can physically damage plant roots. The strong flow may dislodge seedlings or break delicate roots, hampering plant growth or causing plants to die from mechanical stress.
- Excessive Water Turbulence: Too large a pump can cause turbulent water conditions, which can stress fish in aquaponic systems. Fish are sensitive to their environment, and constant strong currents can prevent them from resting, reducing their overall health and growth.
- Potential for Overflow: A large pump may push too much water too quickly into the grow beds or grow trays, overwhelming the system’s capacity. This can lead to spills, leaks, or overflow that wastes water and nutrients, potentially damaging plants or even causing system failure if not managed properly.
- Increased System Wear and Maintenance: High-powered pumps can lead to increased wear on pipes, fittings, and other system components. The extra pressure can stress connections, leading to leaks, frequent breakdowns, and increased maintenance needs over time. This can be especially problematic in DIY systems not designed to handle such high pressures.