Your reef aquarium’s water flow has a cardinal role in maintaining the water environment. It is especially crucial if you have corals.

In the case of fish, a proper flow produces lots of oxygen and gas exchange, helping move nutrients and waste into your filtration system. The flow delivers vital nutrients and food while washing away debris when you have corals.

Most reefers provide water flows running a return pump and powerheads, which is not a mammoth task. But here is the catch. You have to get the correct size of the return pump. There is no place for you to mismatch and make do. That’s why most beginners wonder what size of return pump would they need for their aquarium.

The rule of thumb for reef tanks is to select a return pump to generate a flow rate/turnover of 5 to 10 times the aquarium volume each hour. For instance, if you have a 50-gallon reef tank, your return pump should equal flow rates of 250 to 500 Gallons Per Hour (GPH).

I hope I did not startle you with that abrupt piece of information, especially if you are a new reefer. Even if I did, that was only to give you the core answer to what size of return pump you need for your aquarium.

The rest of the article will give you more details revolving around the question. Keep reading!

What Size Of Return Pump Do I Need For My Aquarium

What Is A Return Pump?

You will hear about return pumps while setting up an aquarium, specifically with a sump. This tube returns water from your filter or sump into the display tank.

That means you basically use it to take the water back to your display of the tank after it drains and runs through the filter. As this course of action takes place, you need to take the tank water back into your display. That is where you need a return pump.

You can install a return pump in a sump or the rear compartment of your all-in-one reef tank.

What Size Of Return Pump Do I Need For My Aquarium?

The size capable of providing a flow rate or turnover of 5 to 10 times the tank water volume each hour is the right return pump for your aquarium.

When a return pump is functional, the plumbing will cause the tank water to run slower because of head pressure and friction loss. That puts the turnover rate between 3x and 7x each hour, which is just the right flow rate.

Ten times per hour is the absolute highest flow through a full-fledged filtration system or sump. However, hobbyists often prefer the latest filtration techniques to run a slightly slower (ranging between 2 to 4 times) tank turnover each hour.

It will lower the dwell time while making less sound. Understand that regardless of your preference for fast or slow water flow, you should take into account your aquarium’s overall water volume to calculate the times your return pump will cycle the tank water.

Here is a point to remember. A tank turnover/hour ranging between 2x and 10x is usually acceptable.

It is material to consider head pressure to gauge your return pump’s capability correctly. You can do the calculation by using a standard formula. Besides, you want to establish some control over your return pump. It is applicable to a DC pump and an inline valve.

The aquarium drain has a maximum flow rate, meaning only a specific amount of water can get through per hour.

Most sumps and overflow boxes demonstrate their maximum flow rates to help you decide the appropriate sump and drain for your aquarium.

The chance of the return flow surpassing the maximum sump/drain flow rate is meager, assuming you will not exceed 10x/hour. Nevertheless, that makes it more reasonable for you to get control over the return flow and the pump size appropriately.

What Is Head Pressure?

It is hard to pump water, considering how the friction and gravity inside a pipe, valves, and tubing decrease the flow rates. The farther and higher the pump pushes the tank water, the more difficult it becomes for the pump to move it, ultimately downturning the flow.

That resistance is head pressure. How powerful it will be depends on the distance and the lift.

If you need a 100 GPH flow rate and select a pump whose maximum capacity is 100 GPH, it will dissatisfy you. The elbows, head pressure, and tubing will have reduced the actual flow rate.

You can use the formula below to calculate the distance, 90-degree turns, and vertical rise to get the amount of head pressure.

  • Each 1 foot of vertical rise equals 1 foot of head pressure. The same goes for every 90-degree elbow fitting. If you get a 45-degree elbow fitting, it will be half a head pressure.
  • Every 10 feet of flat horizontal distance equals 1 foot of head pressure.

What Is Gallon Per Hour?

It is a measurement method for water pumps, short for GPH. You will often notice pumps measured at GPH rates.

Remember that the GPH refers to the maximum flow rate, which is not the case in a real-life scenario. The maximum rate refers to how much the pump will move when disconnected from everything.

You can imagine it as the pump’s flow rate when it is lying in a bowl of water. It is a general standard to measure a particular return pump’s power. However, it will not give you the complete story.

How To Size A Return Pump?

You can utilize the flow chart of a pump manufacturer to calculate the actual flow rate established on the production of head pressure. Pump manufacturers usually supply those graphs or charts to help you get a head start in measuring how you can size your return pump.

You should select a return pump with sufficient power to generate the suggested flow rate based on your earlier calculation considering the head pressure created by your plumbing.

I will give an example where the water increases roughly 4 feet horizontally and 4 feet vertically, passing through a pair of 90-degree elbows. There the calculated head pressure will be around 6.4 feet.

Here is the detailed calculation:

4 feet vertical lift = 4 feet horizontal + 4 feet of HP = 0.4 feet of HP + 90-degree elbows x 2 = 2 feet of HP = Total 6.4 feet of HP

What Are The Types Of Return Pumps?

There are two types of return pumps based on which electricity runs them.

If Alternating or AC power runs them, it is an AC return pump. On the other hand, if it is DC or direct current, it is the other type.

Which One Is Better Between AC and DC Pumps?

Although a DC pump costs more than an AC pump, it is better and more energy-saving. If you look at the energy usage, it will save you a couple of pumps each year, considering you use it above 4 hours per day.

How Much Water Flow Rate Should My Aquarium Have?

The recommended water flow rate for freshwater aquarium is at least 6x the tank volume. So, if you have a 60-gallon tank, you will need a rate of around 200 GPH. Check this article to know more in depth about saltwater tank flow rate.

Can A Return Pump Be Too Powerful For A Fish Aquarium?

A fish aquarium filter, being too powerful, can affect the tank ecosystem negatively. It should be sufficiently strong to provide oxygenation and keep the water clean.
However, if the fish cannot swim comfortably or the water becomes too turbulent, it might indicate that the current created is too strong.

How Often Should I Clean A Return Pump?

If it is a coral reef tank, you should clean the pump once every 2 to 3 months. But twice a year is enough for a fish-only saltwater aquarium.


Do not limit the diameter of plumbing to get the full advantage. If that plumbing tubing falls shorter than the pump’s inlet or outlet (or both), it will restrict the water flow by slowing it down.

The best option is to go with the same diameter plumbing. If the manufacturer recommends something for optimal longevity and performance, stick to that.

On another note, try to keep the pump clean. If you leave it to run loaded with calcareous, it will drastically lower the pump’s performance and lifespan.

Final Thoughts

One thing to understand clearly is that you want to get a somewhat more robust return pump instead of an undersized one. That is because you will always have the option of dialing the water flow down with a controller or valve with a powerful pump. But you cannot notch it up with an undersized one.

Plus, it is never unnecessary to have extra pump energy since that would enable you to add UV sterilizers and reactors without taking the pump away from the display tank. Everything will go alright as long as you make sure the pump fits your filtration compartment or sump system.

That is where I say goodbye today. Good luck!

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