How to Replace Aquarium Substrate


How to replace aquarium substrate? Replacing the substrate in your aquarium has sparked a lengthy debate among hobbyists. Some experts say that getting it replaced can be harmful to your small marine ecosystem because it negatively impacts the bacterial colonies that have already nicely settled on your aquarium bed. These bacteria are responsible for neutralizing the wastes.

While others believe that more of these colonies are on the actual filter, disturbing the substrate is fine if these beneficial bacteria believed to have settled in the filter are not bothered. So, is replacing your aquarium substrate a go or a no? Having a better understanding of your aquarium substrate may let you decide better and have an answer to this question.

How to Replace Aquarium Substrate

Before deciding if you want to change your substrate, you must first learn the proper way on how to replace the aquarium substrate. This process requires preparation because it will surely disturb the fishes and plants in your aquarium.

You need to plan of time if you want to do this. Some materials need to be prepared and pre-changing activities that need to be completed.

Remember that this is considered an invasive maintenance activity. Due to this, you also must plan on when you do this process.

Changing your substrate should not be followed by a filter change or an overall cleaning. Doing so would cause significant disruption to the bacteria that are settled in your media filter. A substrate change and a filter cleaning will prevent them from stabilizing their settlement and keep them from doing their responsibilities to the little swimming colony.

During the actual day where you will be changing the substrate, put your fish on a diet. Don’t feed them, so the wastes they will produce will be minimized. Here are the things and tools you need to prepare when you are planning to change your substrate:

  • Fresh substrate
  • 10-gallon holding tank
  • Cover for the 10gallon holding tank
  • Nets
  • Siphon
  • Water treatment
  • Buckets or cups

The following tasks need to be done in advance:

  • Clean the filter at least two weeks before replacing the substrate
  • Top off the water in your regular aquarium two days before the main event
  • Test the water for nitrite and ammonia levels using a water testing kit a day before the change. Stop feeding your fish too.
  • The day when you are to replace the substrate, set up your holding tank and wash the gravel

At this point, you are ready to follow the steps on how to replace the aquarium substrate.

  1. Turn the filter off from the main aquarium.
  2. Fill your holding tank with about 2/3 water. The water to be used here will come from the main tank.
  3. Empty the main tank from plants, rocks, and decorations. You can transfer to the holding tank or in a temporary bucket.
  4. Put additional water in the main aquarium so the filter can run.
  5. Turn on the main aquarium’s filter.
  6. Start scooping the old substrate out of the main aquarium.
  7. Replace it with fresh gravel.
  8. Set the plants, rocks, and decorations back.
  9. Slowly move the fishes back from the holding tank to the main aquarium.

Replacing the substrate is relatively easy. It just needs proper planning ahead of time.

Frequently Asked Questions


What is Aquarium Substrate?

Right off the bat, you know what substrate is. It’s just it is referred to differently if you are not talking about fishes and tanks.

When associated with aquariums, the substrate is any loose material you use or placed at the bottom of your tank.

Yes, the pebbles and sands are all substrates. Aside from stones and sands, other substrates can also be used. If it covers and makes up the bottom of your fish tank, it is considered a substrate.

Hobbyist usually uses substrates because it adds to the overall aesthetics of the aquarium. It enhances and gives more life to the fish tank. It makes it more real and natural, not just for you but in a way. The Aquarium substrate also recreates the natural environment of the fishes.

Other fish enthusiasts also use substrate to make the vibrancy of the fish pop. An example would be using a black substrate in a tank full of goldfishes.

There are a lot of reasons why you would want to put substrate in your tank. It’s all up to your personal preference.

What are the different types of substrates?

With so many options for substrate plus your creativity, you can create a majestic little marine world. No, you are not just limited to pebbles or sand because you can adapt to your tank because there are several substrates.

  • Pebbles – this is the most extensive substrate that you can use. Pebbles can be out of river rock, glass, quartz, and even colored plastic. Some are even enhanced so they can glow in the dark.

Pebbles tend to be reshuffled by the tank’s inhabitants, and as a result, gaps between the stones will start to form.

The pebble gaps for aesthetics don’t pose much of a problem, but this may lead to uneaten food and fish wastes accumulating in between these gaps. Additionally, it will cause plants to have a more challenging time rooting.

  • Gravel – smaller pebbles, as you may call it, zeroes out the disadvantages of gravel which is the formation of gaps. Maintenance in gravel is also more convenient because there are gravel vacuums that you can use.
  • Sand – yes, this is the same sand you step on and build castles on the beach. You can choose from fine to coarse sand. There are also different colored sands, so you don’t get stuck with just either white or the gray kind.

Sand is a popular choice because it is the most realistic option among the different kinds of substrate. Fishes are very much familiar with sand, so if your goal is to create a habitat that is like their natural ones, then sand is your best bet.

  • Soil – you might be a little hesitant with this substrate because what your thinking is soil with water equals mud, and you don’t want a muddy and dirty-looking tank.

It’s just not you who don’t like muddy water because your waters would get stressed about it too. So, fish stores would usually have a soil substrate formulated where the soil won’t mix with the water and vice versa.

How deep should my silver sand be?

It is recommended that for sand, the depth of the substrate is 1-inch to 1.5 inches.

How deep should my gravel be?

When using gravel, the depth is more in-depth compared to sand. You should aim for a substrate level of 2-inches and even more, especially if you have live plants in your marine ecosystem.


Replacing your aquarium substrate is entirely safe and should not cause too much stress to your fishes only if it is done correctly. It should also be seamless maintenance work for you.

Your fishes will thrive better knowing that they are not swimming with any unnecessary dirt that the bacteria can’t handle. Again, it is just a matter of planning with great timing when replacing your substrate.

You can choose from any of the substrate types and further enhance the beauty of your fish tank while providing a home that is conducive for your little swimmers.

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