How Often Should You Do
Aquarium Water Changes?
How often should you change your aquarium water? This is one of the most common questions aquarium owners have. First of all, it doesn’t matter if your aquarium is a freshwater aquarium or a saltwater aquarium. And it doesn’t matter if you have plants or corals.

For info on how to do water changes, please read “Aquarium Water Changes: Making It Simple”.

How Often and How Much?
We recommend changing no less than 1/3 of your aquarium water once per month. This is a good minimum level of water changes in order to make sure you have a healthy aquarium.

What If You Want to Change Less Water?
You can change less than 1/3 of your aquarium water at a time, but make sure the total of your water changes in a one-month period is 1/3 of your aquarium water. With a 60-gallon tank, you could change 20 gallons once per month, 10 gallons every other week, or 5 gallons every week and you would satisfy the requirement to change 1/3 of your water every month. With small aquariums, a larger water change once per month is easy, but with larger aquariums splitting up the water changes into smaller weekly amounts is usually easier.

What Happens If You Change Water Less Than Once Per Month?
We strongly recommend you change at least 1/3 of your aquarium water each month. Fish waste and uneaten food will start to accumulate in the aquarium gravel and in the aquarium filter. Sucking the waste out when doing a water change with a gravel vac is the best way to stop the waste from becoming an issue.

Additionally, chemicals can accumulate in the water over time. This can come from by-products in aquarium additives or minerals in the tap water used to top off the aquarium. Keep in mind that when the water evaporates only the water is removed--all the minerals stay behind. If the water is never exchanged the chemistry of the water will be out of range, causing problems for the health of your fish, plants, and corals.

Is It Useful To Change More Than 1/3rd of The Water?
Changing 1/3rd of your water once per month is the minimum. It is very common for fish breeders or people medicating or conditioning fish to change water daily. We do recommend that you change no more than half of your aquarium water at one time to prevent the shock that can come from changing too much water at once. Always make sure that your new water is as close as possible to the same temperature, salinity, and pH of your old water.

Is It Sometimes a Good Idea to Do Large Water Changes?
If your aquarium has an issue such as an algae problem, or it is very dirty because of neglect, you may need to do more water changes for a time to get it back on track. Doing a series of 50% water changes daily to fix a problem is not uncommon. Keep in mind an ounce of prevention is worth a pound of cure. Once the aquarium issue is taken care of, you will no longer need to do water changes this large this often.

For info on how to create the best water for water changes, please read “It All Starts With Water”.