How to Change the Water in Your Aquarium

Why do we need to change the aquarium water?

Even if the water looks clean, stir it up on the surface and you will be shocked with the amount of dirt. Where does it come from? During the feeding process, small particles of food fall to the bottom of the tank and decompose. In the meantime, eaten food is accumulated in the tank in the shape of urine and feces, which also produces dirt.

Aside from the unwanted waste which is visible to the eye, there is an invisible one in the form of nitrates and phosphates. They are damaging to the fishes and make them more susceptible to illnesses. The rise of nitrate levels will slow down the growth of young fishes and can even result in a decrease of reproductive functions with adult fishes.

3D aquarium background in a wall mounted fish tank

Nitrates also affect the development of algae. Phosphates have a similar effect. Water replacement is the best way to maintain the levels of phosphates and nitrates low. Waste isn’t the only reason you should change the water in the aquarium. Minerals are important for the health of your fishes as well as the stable chemical composition of the water. 

In time they are either used up or filtrated. If you don’t replace them, the pH level will drop. Besides, the lack of minerals will affect the strength and health of fishes negatively. Regular water replacement can be compared to giving kids vitamins which help them maintain their strength and health. 

How often you should change the water in the aquarium?

Water replacement should be a part of the regular maintenance of the tank. How frequently you will do it depends on many factors. Smaller tanks with more equipment will require you to change the water more often than the bigger ones with less equipment.

It is advised to change 10-15% of the water every week. If you have a heavily equipped tank, you should change 20% of water per week. Less equipped tanks can last up to two weeks but that is the limit you shouldn’t go over.

If you are not sure if you are using the right aquarium equipment for the size of your aquarium, we wrote an article about aquarium equipment that should be helpful to you.

Some people think that adding water into the aquarium is the same as changing the water. However, that is not the case. Adding water doesn’t remove the waste so don’t fool yourself thinking that it is clean only because you added fresh water into it. This is a common beginner’s mistake, check out others mistakes people make with new aquariums in case you might be making one of those.

how to change water in aquarium

Tips for changing aquarium water

There are some pieces of advice you should consider when changing the water:

  • Let the water sit – this way dissolved gasses that are dangerous for the fishes will decompose. That will also help the pH level stabilize before the fishes are added to the aquarium.
  • Clean the sand – When you change the old water, vacuum the substrate at the same time. That way you will get rid of the waste.
  • Don’t clean the filter – Cleaning the sand affects the colonies of healthy bacteria. The filter is another location where these bacteria grow. It wouldn’t be wise to clean both locations at the same time. The filter can be cleaned in between water replacement.