How to Determine GPH Water Flow Rates

How to Determine GPH Water Flow Rates?

How to Determine GPH Water Flow Rates?

Some people are very keen to know about the gallon per hour water flow rate in their fish tank. The flow rate depends upon the pump you are using in your aquarium.

The filter and pump you use for tanks comes with a flow rating in gallons per hour. However, different types of barriers can lower this rate.

These barriers can be canister filter, sponge filter, and some other. After installing the pump, you can test its flow rate.

Many people do not know how they can measure this flow rate. is here to guide you straightforwardly.

If the flow rate is high, the gas exchange is also top, which is suitable for an aquarium. Carbon dioxide releases from the water surface and oxygen come inside. 

Fish live in a comfortable environment when there is enough oxygen in tank water. Fish stays healthy and active in oxygen-rich water.

You can easily determine the GPH flow rate of water in your tank. Just take out your aquarium pump and turn it on in some water container. Now run the pump and calculate its speed by which it moves the water, this is how you can measure the GPH flow rates easily.

What is the Meaning of GPH?

GPH stands for gallons per hour. It is for the denotation for measurement of flow rate of water in gallons.

Aquarium Pump – GPH Water Flow Rate Chart

Here is a chart showing flow rates by different pumps according to pipe size.

Pipe size Flow rate
½ inch 200
¾ inch 400
1 inch 600
1.25 inch 1000  
1.5 inch   1400
2 inch 2200
2.5 inch 3200

How to Determine GPH Water Flow Rate?

Water flow in the tank is significant, and a healthy tank GPH water flow rate is 6 to 10 times per hour in one to ten rating. 

Some people think that it should be more than this, but indeed it is an excellent rate.

First of all, you should know how many gallons of water are present in your tank. Then use the flow rate and water capacity to measure how many times per hour, the flow rate is.

Step by Step Guide for Calculating GPH of Aquarium Water 

In these straightforward and easy steps, I will guide you through calculating the gallons per hour flow rate of your aquarium water.

Step 1 – Prepare a One Gallon Container 

First of all, prepare a one-gallon container so that every per gallon can be measured. The box must be clean and sterile.

Take water in this container from your tank, and you can put it back into your tank so that water levels should remain maintained. 

Make sure that the container is of just one gallon so that you can do the easy and quick calculations. 

Step 2 – Turn On the Pump

Now, take out your water pump from the aquarium and put it in the container to check its flow rate quickly. Otherwise, you can check it inside the aquarium, but fish get disturbed. 

So that is why we prefer separate equipment. The pump should be off at first. Then put the pump inside the container. 

Keep the pump inside and attach its plug to the outside power source. Do not let its wiring to become wet and ensure excellent safety. 

Now, connect a plastic pipe to the nozzle of this container. Insert the other end in this container so that the pumped water came back to it. 

Now, it is time to turn the pump on and check its flow rate. 

Step 3 – Note the Readings from Stop Watch 

Start a stopwatch immediately as the pump is on and note the readings. You can take the digital stopwatch or the other one, whichever is available.

Step 4 – Do Some Calculations

Consider, for example, you get the value 20 from your stopwatch. It means that your pump can fill a one-gallon container in 20 seconds. 

Now, divide this time by 60, like 60 divided by 20 is 3. It is your gallon per minute rate.

Now multiply it with 60 to get the gallon per hour rate, three times multiply by 60 is equal to 120. 

Step 5 – Put the Pump Back in Aquarium 

Now put the pump back into the aquarium. Take the pump out of the container safely by first unplugging it.

Restart the pump in your fish tank and pour the water back into your aquarium. 

Is there a Need to Change the Pump to Determine GPH Water Flow Rate?

A standard GPH rate is 120; if your pump is pumping less than this value, then you need to change your pump for sure.

If the rate is higher than this, than it is excellent, the GPH rate depends upon the pump size and even the aquarium.

You will buy a big pump for a big aquarium whose GPH rate will be high while a small pump is for small aquariums, and GPH rate is low accordingly.

But it should not be less than 120; otherwise, the pump is of no use. If your pump is pumping very little water, then change it. Otherwise, there is no need.

However, a big pump for big aquariums has GPH rates near 400, which is good. 

Which Aquariums Need High Flow Rate and Which Needs Low?

That aquarium needs a very high flow rate, which is big and has big fish in it. The big fish need more oxygen; definitely, that’s why the flow rate should be higher.

The reason behind it is that the more the flow rate is, the more water gets enrichment with oxygen. More oxygen is a requirement for these big fish.

But the aquarium, which is standard, medium-size or small, which has small fish in it, does not need such a high amount of oxygen. 

Oxygen is essential for the breathing of every living organism, but small fish need oxygen according to their body needs and size.

So it is good to have a reasonable flow rate, neither too high nor too low as I have told you that 120 GPH is a perfect flow rate for medium-sized aquariums. 

While big aquarium pumps should have 350 plus gallons per hour of flow rate. 

If there is any case like your fish is in stress or shock conditions, you can add two pumps in your aquarium to increase the flow rate to a large extent. 

It will help to give more oxygen to your suffocated fish and revive it back to its beautiful life.

Suitable pumps are very beneficial for aquariums. Most of the high-quality water pumps are efficient in their work and create a reasonable water flow rate. 

There are many new and advanced pumps on which flow rate is already present. High-pressure pumps are exquisite, while low pressure pumps on not so good.

A right pump flows a reasonable rate of water, then the aquarium filtration system also stays good. More water flows from the low levels of aquarium and water comes up, as a result of this ammonia is filtered completely.  

Aquarium habitat also remains fresh, active, and healthy enjoy their life to the peak. So, buy a suitable pump for your aquarium, which has a reasonable flow rate so that you can enjoy seeing your fish happy end active playing all around. 

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