The importance of water changes in the home aquarium

by Christopher Fong


photo provided by Absolutely Fish


Water changes provide many benefits to most home aquariums by adding essential minerals/elements and removing organic/inorganic toxins that can build up over time in a closed environment like an aquarium. The concept of adding “good stuff” and removing “bad stuff” can be the difference between a successful long-term aquarium and a problematic aquarium where the aquarist constantly battles nuisance algae and disease. The benefits of water changes can be applied to all different types of aquariums ranging from a simple 10-gallon freshwater community tank to a 150-gallon reef tank. However, certain aquariums benefit more from regular water changes such as African cichlids, goldfish, Discus, saltwater fish only and large predatory tanks. Water changes become especially important in tanks where filtration is undersized, the fish population is overstocked and overfeed. However, for water changes to be effective they must be done correctly regarding frequency, size, and preparation of the new water. In this blog I will discuss how to correctly perform a water change to help benefit your aquarium during maintenance.

Frequency: How often an aquarist must perform water changes on their aquarium varies depending on several factors regarding the way a tank is setup and stocked. For example, a 75 gallon with overstocked large predatory fish and an undersized hang on back filter rated at 30 gallons is going to need more frequent water changes compared to a 20 gallon with an oversized hang on back filter rated at 75 gallons stocked with an appropriate amount of small community fish. Water changes also vary depending on people’s schedule between family, work, and school. Personally, I recommend water changes be conducted every week for most types of aquariums. This helps to keep the amount of organic and inorganic impurities limited in the aquarium as these toxins can have a negative effect on the health and growth of fish/ corals and can also promote the growth of nuisance algae. Another benefit of doing frequent water changes is the addition of essential major, minor and trace elements that can help maintain proper water parameters and keep the organisms within the aquarium healthy. With doing regular water changes the PH of the aquarium also remains more stable with the addition of carbonates/ bicarbonates and the removal of organic wastes that can acidify the water overtime. In a scenario where an aquarium receives a water change once a month the aquarium will often experience a drop in PH due to the build up in organics until the next water change where the PH will then suddenly rise with the addition of new water containing a higher PH. This shift in parameters can cause stress upon the organisms within an aquarium compromising immune systems and enabling disease to take hold. Once again, every aquarium is different and different water change schedules can work equally well ranging significantly.   

Size: Once again, the size of a water change depends on a variety of factors depending on how a tank is setup and stocked. Some aquarist will prefer smaller more frequent water changes while other prefer larger less frequent. But what exactly constitutes a small and large water change?  This varies from person to person, but I believe water change sizes should be categorized as:

Small: 10-25% of total aquarium volume

Medium: 25%-50% of total aquarium volume

Large: 50%-75% of total aquarium volume

With this guideline established, most people should be doing small/ medium sized water changes on their aquariums depending on their stocking levels and filtration setup. Personally, I believe a good percentage to aim for is around 30% as this size water change can remove sufficient amounts of organic and inorganic impurities a 10% simply cannot. This size water change can also add sufficient amounts of major, minor and trace elements need for proper health/growth of aquatic organisms.

Additional notes: As already noted size and frequency of water changes performed on aquariums varies depending on many factors including but not limited to:

-Size tank

-The Age of the aquarium

-Type of filtration equipment

-Type of aquatic organisms being kept (regarding amount of waste produced and desired water chemistry)

-Number of aquatic organisms being kept

– The addition of supplements

-The frequency of cleaning (Filter/Substrate)

If you would like to see a demonstration on how to perform a water change and to clean your filter/gravel bed. Please stop by the store and an associate will be happy to show you!