How to Change Aquarium Substrate (The Right Way)

Owning fish or any other kind of aquatic life means that you have to invest a certain amount of time and energy into your aquarium’s maintenance.

An unhygienic aquarium can lead to several problems for your fish, the plant life, and can clog your filters as well.

While not everyone agrees on regularly changing the aquarium substrate, it is done quite often.

You will need to prepare a bit beforehand—such as finding a place to relocate your fish while you are changing the substrate.

You’ll also need to time the change so that it doesn’t coincide with a filter change or tank cleaning.

Here’s what you need to know about changing the aquarium substrate.

What Do You Need Before the Changing Aquarium Substrate?

To make sure nothing goes haywire at the time of the change, make sure you have everything you’ll need beforehand.

This includes another fish tank or a tub to keep your fish while the change is taking place.

If you do opt for a plastic tub, make sure it hasn’t been used for cleaning and has traces of bleach or cleaning agents.

You’ll also need to ensure that you haven’t recently changed or cleaned the filter.

If you’ve just changed or cleaned the filter—a substrate change could make it difficult for the filter bacteria to adjust to the changes.

To be on the safe side, clean the filter a minimum of 2 weeks before you plan on changing the gravel.

Additionally, in the last couple of days, before you go ahead with the substrate change, you should fill up your tank completely.

Then, check to see if the levels of ammonia and nitrate are at zero. If they are, you can proceed with the change.

If they aren’t, you will have to correct this issue before you change your gravel.

Finally, try not to feed your fish the day prior to the change. This makes things easier for you and lessens the chances of waste collecting in the temporary tank.

If you do feed your fish, they’ll produce waste in the other tank and make it difficult to clean up after.

It’ll also create a dirty environment for the fish to have to spend at least a few hours in.

What Do You Need to Do During the Change?

Now that you’re ready to proceed with the change, it is time to prepare the temporary tank.

Take water from the main tank and add it to the temporary tank.

The tank should be around ten gallons, so fill it a little above the halfway mark to ensure that there is enough water for your fish.

Using water from the main tank makes it easier for your fish to adjust to the change.

Next, move the live plants, rocks, and any other aquarium fixtures you have from the main tank to the temporary one.

Moving the live plants can be a challenge, so make sure that you don’t damage their roots or kill the plants in the process.

The benefit of moving these fixtures and plants to the temporary tank is that they’ll retain the bacteria that grew on them in the main tank.

This makes it easier for the tank to resume its original environment once you are done with the substrate change.

Before you move water from the main tank to the temporary tank, turn off the filter. Place the fixtures in the temporary tank before you move the fish.

Once you’ve moved the fish, you will have to close the temporary tank so that your fish can’t escape.

Because your makeshift tank could be a tub or another container, you can use cardboard or another covering to close the top.

If you are using a proper tank as a temporary tank, you won’t have to face this issue.

An extra tank may actually be a good investment, as you can use it to keep sick fish to prevent them from spreading their illness to other inhabitants of the tank.

They’re also more convenient if you need to keep your fish out of the main tank for several days.

Now that the water level has receded in your main tank, don’t try to add more.

The lower water level will make it easier for you to scoop out the present substrate.

Just make sure there is enough water in the main tank for you to switch the filter on again.

Changing the Substrate

You’re now ready to change the substrate. Scoop out the gravel from the aquarium and place it in a large bucket.

Clear out the entire surface of the tank and then clear up the remaining debris as well.

Wash the gravel with clean water until the rinse water is clear.

Dirty gravel can introduce unfamiliar bacteria to your aquarium and harm your fish—so make sure it is thoroughly rinsed before adding it into the tank.

Pour in the new gravel. The level of substrate is usually 2 inches or sometimes more when you have live plants that need enough substrate to take root.

Transfer the plants and fixtures back into the main tank once all the new gravel has been added. Add the fish, with the water, back into the main tank.

Let the lights stay on the first day of the change—this helps you identify if any of your fish haven’t adjusted to the change and are feeling ill, or if the water looks dirty or harmful.

Once you’ve transferred the fish back into the tank, don’t feed them too much right away.

They might even need a stress coat in the water to help them settle down. If you feed them too much when they are in discomfort, they could fall ill.

If everything goes well, you can resume your regular light timings and feed your fish the way you usually do after one day.

Check the water for ammonia and nitrate levels.

A slight rise is alright since you have just changed the gravel.

However, if after 2-3 days they still haven’t gone back to zero, you will have to treat the tank until the levels go back to zero.

What Other Things Should You Keep in Mind?

When changing the substrate, you may be tempted to change a little bit of it at a time to maintain the nitrifying bacteria levels of the water.

However, the nitrifying bacteria usually live in the filter, not the tank. It is a better idea to clear up all the substrate completely and replace it with new material.

Make sure you vacuum out all the debris left from the old substrate before you bring in the new substrate.

It isn’t necessary to remove your fish from the main tank before making the change, however, it can be harmful to leave them in as well.

Unless you are an experienced aquarium fish owner, you could hurt the fish while adding in the new gravel.

While it is stressful for fish to have to transfer to a new tank for a temporary period, it may be the smarter choice to make.

Before you add the new substrate, let your aquarium sit for a while.

This helps clean out any sand or debris that was floating around in the water settle it back down so you can vacuum it out.

How Often Do You Need to Change the Aquarium Substrate?

With newer filter technology, you actually don’t need to change your substrate very often.

You can even go for several years without feeling the need to do a substrate change.

Unless there’s a problem with the substrate you currently use—or if you want to change, for example, from gravel to sand, changing the substrate is a rare occurrence.

You might need to change the substrate if you get live plants that require a soil bottom rather than gravel, or if you are changing the kinds of fish you have.

For example, bottom-dwelling fish may need a smoother substrate so they don’t get injured from any sharp gravel.

Another reason to be changing substrates is if you are attempting to pair multiple substrates together.

Some tank owners pair soil and gravel together. This helps the soil stay grounded while having an aesthetic appeal with the help of the gravel.

Improper tank maintenance can lead to the dirty substrate.

This can harm your fish, make it difficult for your live plants to thrive, and can become home to dangerous bacteria. It can also affect the water pH level of your tank.

Therefore, if your tank water is changed regularly and you have an exceptional quality filter, you won’t have to change the substrate for a few years at a time.

What Kinds of Aquarium Substrates Are There?

There are several options for aquarium substrates.

It doesn’t necessarily have to be gravel and pebbles—although that is one of the most common options.

It can also be sand, soil, or water-changing substrates that maintain the pH level and texture of your water.

Final Words

Changing the substrate of your aquarium takes around two hours if you do it in one go.

As long as you have all your equipment and an extra tank prepared beforehand, you shouldn’t face any problems.

Be sure to keep a careful eye on your fish once they move back to their original tank.

Some fish experience more stress than others and may need extra attention to adjust to a different environment.

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