Filter Flow Rate Guide – DPH Definition & Turnover Rate

There are many factors included when it comes to deciding on the right aquarium filtration. The importance of a proper filtration system cannot be stressed enough. If a filtration system works well, the environment is more likely to be great for your fish; if it doesn’t, a wide range of problems can occur.

In general, the filtration system is tailored based on many factors such as the type of fish you plan to keep, the aquascape, the size of your tank, and other factors. In this regard, there are some filter performance indicators that can help you chose the right setup.

One of the most important things to consider when choosing the filter for your aquarium is the filter flow rate. Great filter flow rate and efficient water movement throughout the aquarium are key to maintaining healthy environment for your fish.

While the filter flow rate is easy to understand, what’s difficult is to come up with a plan on how much GPH you need for your specific setup.

This depends on a lot of factors and here are some guidelines that could simplify the matter.

Aquarium Filter Flow Rate

Defining GPH

GPH stands for “gallons per hour,” which in general refers to the flow rate of filters. It shows the maximum number of gallons of aquarium water flowing through a filter in one hour. Based on filter strength, filter type, efficiency, and state, the GPH greatly varies.

The entire volume of aquarium would typically run through the filter several times in one hour. The higher the GPH the better, but you shouldn’t exaggerate as too much flow means more water movement.

This is bad for some fish that don’t like as much current such as betta fish, so it should be avoided.

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Turnover rate and GPH

Turnover rate is often considered as a synonym for GPH. However, this is far from true as turnover rate is completely different; turnover rate describes the true efficiency of a filter.

Not all water in the aquarium is magically going to end up in a filter. Even more, some water filtrated and introduced back to a tank is going to get sucked right back in and filtered again immediately.

Water in ‘dead spots’

On the other side, some water in “dead spots” has a significantly lower chance of being efficiently filtrated. Dead spots can lead to water becoming stale and is a perfect environment for unwanted organisms to grow. These organisms can harm your fish, cause infections, and create a wide range of other issues.

If the filtering system is efficient enough, this problem is minimized or even completely avoided.

For example, a filter that has a stable 100 GPH may be assumed to have the strength to process all of the water in a ten-gallon aquarium in one hour for 10 times.

However, this is not accurate since the more detailed the aquascape, the bigger the inefficiency. Rocks, plants, caves, and other decorations are a major problem for efficient filtration.

If your aquarium is highly decorated, you may want to introduce more than one filter in order to resourcefully deal with dead zones.

In conclusion, the two most important factors to consider are filter flow rate as well as the true efficiency the filtering system provides to your aquarium.

Benefits provided by good filter flow rate:

  • Increased oxygen levels as a result of better water movement across the surface
  • Good waste removal as a result of proper and timely filtration
  • Improved water movement across the aquarium, which prevents dead zones
  • A more natural environment provided by a current created by filtering system
  • Better overall water quality and easier tank maintenance

Determining the right filter flow rate for your aquarium

There are a lot of different opinions when it comes to determining the exact GPH needed for superior water quality. In reality, it all depends on diverse factors.

Not all aquariums are equal and something that works for one aquarium, might not work for others.

First off, different fish species prefer different current speeds. Some fish prefer more current, while others, like bettas, prefer calmer waters since a strong current could stress your fish.

Some tanks contain more decorations whereas some are simple and plain. Sensibly, the more obstacles in the water, the more potential for dead spots.

For example, tanks with live plants are better with lower GPH meaning less surface water movement to keep more CO2 in the tanks needed by plants.

Fish-keeping experts claim your filtration system should be able to turn over the entire aquarium volume at least four times per hour. If you are not hindered by factors listed above, you should definitely aim for the highest GPH possible.

There are also a lot of opinions concerning your filter’s ability to turn the entire volume of the aquarium 6 or 10 times per hour.

All this being said, it should be clear that there are many “rules of thumb” for GPH in the aquarium world. The best thing you can do is thoroughly examine your precise needs for water filtration.

Most of the time, aim for the higher GPH and find what works best for your specific aquarium. And keep in mind. Don’t fix it if it’s not broken!

4 thoughts on “Filter Flow Rate Guide – DPH Definition & Turnover Rate”

  1. Would two Aqueon quiet flow 20 in a 45g tank be two strong for my angelfish and will it be good enough to filter my tank I had an Aqueon 75 and water flow was killing my fish

  2. Hi, unfortunately I can’t see how old this post is, but is there a way I could find out the rough GPH of a filter that doesn’t have it labelled on the box? For example, if I use a sponge filter and air pump?


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