When Should You Do the First Water Change in a New Aquarium?

Estimated read time 5 min read

Wondering how long you should wait before carrying out the first water change in your aquarium?

You should do the first water change in a new aquarium after about two weeks or 15 days since you set it up and started using it. You should only change 20-25% of the water at this stage. After that, you can change it earlier only if required.

To learn more about when you should do the first water change and things you should account for, you can go through the following sections.


Carrying Out the First Change

The first water change can be an important one since it can mean that your new aquarium or fish tank and the fish in it have had enough time to settle and get used to the conditions of the aquarium.

Since you are likely to be a new aquarium owner or fish parent, you should take some time to figure out when exactly you should carry out the first water change.

You might think that you need to replace the entirety of the water content in your aquarium the first time around, but you should only change it partially so that it doesn’t end up being too much too soon.

One of the main things you should carry out is to set up your new aquarium properly with the substrate, suitable water, and the right kind of equipment in place.

Wait for 24 hours before adding the fish, and then wait for another two weeks to carry out your first water change. You can figure out the process of carrying this out through.

Things to Look For

Although you should generally wait for two weeks or 15 days to carry out your first water change, several things can affect this period and several factors you should learn about and account for.

You can go through some of these below.

Bacterial Bloom

Bacterial bloom is a common and healthy occurrence in your new aquarium. There is usually a specific period following the introduction of your fish to the new fish tank or aquarium.

Healthy bacteria will begin to grow, develop, and establish themselves in the aquarium within this kind of bacterial bloom.

During these few days, you might notice that the water in the tank is turning murky and milky, but this is entirely normal. You should not disturb the water at all and wait it out.

The water will clear all by itself and will make your fish healthier and more settled.

Nitrogen Cycle

When it comes to the nitrogen cycle in a new aquarium, the process involves converting the ammonia in the water into nitrates that can make the water clean, safe and healthy all on its own.

This kind of cycle tends to come about due to the established ecosystem between the plants, fish, and water, resulting in a generally slow process that removes and converts the waste in the water into healthy substances.

Usually, this process can take a few months. However, if you purchase a starter kit from a store, you might be able to complete the process sooner. In this case, you might need to change your water partially within a week or two.

Ammonia Levels

There are bound to be waste elements inside your aquarium due to the excretion mechanisms of your fish, along with the proteins that might be present in the water.

Usually, bacteria present in the water can convert these into ammonia, harming your fish. However, other healthy bacteria can help you convert this ammonia into nitrites and then into nitrates.

However, if, for some reason, this kind of conversion process is not taking place as it should, and if the ammonia levels are abnormally high, you can change 20-25% of the water a bit sooner than two weeks.

Make it a point to monitor these levels regularly.

Dirt and Debris

Over time, dirt and debris will also collect in the aquarium’s water. These can often enter the aquarium or tank externally when you open the tank, even if you always leave the tank open. This is nearly impossible to avoid considering that you will need to open the tank frequently.

Even when you feed your fish or try to adjust some equipment, you might introduce dirt to the water if your hands are dirty.

Over time, these can gather in the aquarium and affect the quality of the water. Usually, your filter will help keep this in check, but you will need to carry out a partial water change once two weeks are up.

Altered pH levels can affect this, so make sure you keep these consistent.

Should You Replace All the Water?

For the first water change, you should not replace all the water. Only replace 20-25% of the water, depending on the size of your aquarium. Even regularly, it would help if you carried out only partial water changes since complete water changes can damage the health and safety of your fish.

Water Changing Frequency

Now that you know when to carry out the first water change in the aquarium, what about the subsequent times? This depends on your aquarium’s size, but you should carry out partial changes once every week or two.

Make sure you use the same kind of water and carry out the necessary dechlorination and filtration processes to ensure consistency.

Summing Up

After setting up your aquarium, you should do your first water change after two weeks. After that, do not change the water entirely but only replace 20% while ensuring consistency in the water you add. You can carry out the changes once a week or every two weeks following this point.

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