The frequency of water changes in your fish tank comes down to multiple factors. Ultimately though, it comes down to personal preference.
In this article, we will discuss the things you should take into consideration when deciding how often you should do a water change, and how much of the water you should change.
Why Water Changes Matter
In nature, water is constantly circulating out from various places, and it’s getting a lot of new water as it loses that old water. Not only that, but the ratio of waste to water volume is much different than in an aquarium.
Closed System Nitrogen Build-Up
In an aquarium, we have a closed system that does not receive new water and circulates out the old water like in nature. The nitrogen load in a closed system with a much smaller waste-to-water volume ratio is even harder for a heavily planted tank to keep up with. As we covered in our nitrogen cycle article, bacteria break down fish waste into a non-toxic nitrogen compound called nitrate. However, at high levels, it’s still not healthy for fish, and most bodies of water in the wild will have very low or no detectable levels of this. So, by doing a water change, you are diluting this compound.
Chemicals & Toxins
In addition to nitrogen, we also introduce a lot of different chemicals and waste products into the water. Think about all the ingredients in fish food like food coloring, preservatives, or byproducts. Even things from our hands like soap, lotion, and other potentially harmful chemicals.
TDS Buildup
Lastly, if you simply top off your tank when it evaporates using tap water, you’re actually doing the water a disservice. Water contains many dissolved solids that do not evaporate with the water. Over time, these dissolved solids such as calcium, sodium, magnesium, or nitrate build up to extreme levels. Have you ever wondered why the Great Salt Lake in Utah has a salinity level more than twice that of the ocean? It’s because the lake has no outlet, so it just continues to build up.
Water Change Frequency & Amount
As I mentioned at the beginning, the truth is that the amount you change your tank water comes down to your personal preferences.
As a Blue Ram breeder, I can personally say that my fry tanks oftentimes receive a 90% change every day. I have personally witnessed faster fry growth doing this versus only once or twice a week. Not only with breeding, but when I do frequent large water changes in any of my tanks, my fish are so much more vibrant and healthy, my plants look better, and the water is always crystal clear.
This brings up another issue I hear a lot, “water changes are stressful and they can harm fish”. Let’s set the record straight about this, INCORRECTLY doing a water change can stress or harm fish, but not if you do it correctly. To correctly do a water change, it’s absolutely essential to match the new water temperature to the aquarium water.
I’m a firm believer in water changes multiple times a week, especially if your tank is not heavily planted and you are moderately to heavily stocked. I do a minimum of 50% once a week, but I try to aim for twice a week.
As a general rule, the average aquarist should aim for a 25-50% water change once per week.
If you are a heavy feeder, have a heavily stocked tank, or you are breeding fish, it might be beneficial to increase the frequency.
FAQ
How can you make a tank need less water changes?
First, you should feed foods that don’t release a bunch of stuff that stinks up your tank and clouds your water, such as high-quality pellets instead of flake food. I use the Hikari brand. Most importantly, stop overfeeding! Almost everybody feeds way too much.
The other way is to keep your tanks planted. This will reduce the amount of nitrate buildup in the water, which means fewer water changes you need to do to remove this. They also absorb a lot of other dissolved solids.
Do water changes stress fish?
As long as you do them correctly, it will cause minimal stress. You should always match the temperature of the new water and use a water conditioner before the new water is added.
How long can you go without a water change?
Probably a very long time, a lot of people never do them, but as we have discussed, it’s beneficial to do them.
Summary
The frequency of water changes depends on multiple factors, but mostly it comes down to your personal preference.
As a general rule, for the average aquarist, 25 to 50% once per week is recommended. If you feed heavily, you have a heavily stocked tank or your breeding fish, you may need to increase the frequency.
To make your life so much easier, you should invest in the python water changer and say goodbye to carrying heavy buckets of water one at a time.
