Best Aquarium Substrate: Guide to Gravel, Sand, Soil & More

What is an Aquarium Substrate?

Aquarium substrate is the material that is used to cover the bottom of the aquarium. There are many types and colors of aquarium substrate that are either beneficial to the aquarium, necessary for the fish, or provide a pop of color that adds instant beauty. It is important to choose the correct substrate for your aquarium as it can greatly impact the water quality. It helps by acting as a natural filter for your water. Substrate can help collect organic waste which will then provide food for aquatic plants

There are many different types of aquarium substrate that you can safely use in your aquarium. It depends on the fish that you keep which substrate works best. Different species of fish have different substrate needs, so it is best to do your research before you make a decision on which type you choose which  substrate is right for your aquarium.

There are two different kinds of aquarium substrate, inert and active. Inert substrate is helpful to your aquarium without changing the water chemistry or the water quality. Active substrates can alter the water chemistry and quality of your aquarium.

Aquarium Substrate
Aquarium Substrate

What is the Best Aquarium Substrate for Your Tank?

When choosing substrate you will want to make sure that you have looked at the needs of the fish and plants that you are planning on putting in your aquarium. Different fish and plants will have different requirements to thrive. For example, bottom dwelling fish that root through the substrate for food will do best with a fine, soft sand or gravel. Anything that is rougher could potentially cause injury to your fish. If your tank is heavily planted, you may want to choose an aquarium soil, clay, or mixture of the two for your substrate.

Keep in mind that some types of substrate will change the pH of your water. These types of substrates are called active substrates. Some active substrates are limestone gravel, and aquarium soil.

Aquarium gravels are typically hailed as the best substrate for your aquarium for their versatility, but they require regular cleaning. The same goes for lava rocks, and pebbles.

Whichever substrate you decide, remember to monitor your water parameters, and establish a regular water cleaning schedule so that you can identify and correct any issues before they become major problems.

Why is Gravel the Best Aquarium Substrate for Most Tanks?

Gravel is usually the best choice for freshwater aquariums. You can get gravel in many different sizes and coloration to suit your aquarium and provide a beautiful background for your fish. Gravel can be a type of inert or active substrate depending on the type of rock that it is made from. For example, limestone gravel can affect the pH of your aquarium by making it slightly higher.

Gravel as a substrate for aquariums has a nice flow through it. Unlike sand or clay substrates, this allows for there to be no buildup of harmful bacteria or gasses that could potentially harm your plants or fish.

Gravel is great for aquarium plants too, allowing plenty of space for the roots of the plants to grow through and not become impacted. Gravel is one of the most popular choices for substrates for the home aquarium as a stand-alone substrate, mix-in with another substrate, or layer above and below another type of substrate for support.

For most aquariums, Seachem Chlorite Black Clay Gravel is the best aquarium gravel. It not only provides the aquarium substrate with the support that it needs to grow beautiful, large plants, but each piece of the clay gravel is porous to allow for the growth of beneficial bacteria for the plants. The black color allows for anything you pair with it to stand out and become more vibrantly visible against the dark background.

Another great thing about Seachem Chlorite Black Clay Gravel is that it is not created with chemicals, so it will not alter the pH of your water. Seachem Chlorite Black Clay Gravel, when taken care of properly, shouldn’t need to be replaced often if ever.

What is the Best Aquarium Substrate for Planted Aquariums?

Depending on the type of plants that you are placing in your aquarium, you will want to consider the substrate carefully. Certain kinds of substrates such as clay or sand will pack down over time and can suffocate the roots of the plant and prevent them from growing to their full potential.

Gravel is considered one of the best if not the best aquarium substrate for planted aquariums because the spaces in between the gravel pieces allow for roots to grow and receive the proper aeration without packing down. Gravel substrate also allows for the growth of beneficial bacteria without the risk of harmful buildup of waste or gasses.

Gravel substrate is also a great choice because it will not alter the pH of the water unlike other substrates that are marketed for planted aquariums.

Why is Aquarium Soil the best for Planted Aquariums?

Aquarium soil is best for planted aquariums as it is specially created for aquariums so that it doesn’t mix as easily in the water to create a muddy, cloudy mess. It is not advisable to take soil from outside and place it in your aquarium as it could house contaminants, or bacteria that could harm your plants or fish. Aquarium soil is an active substrate. This means that it will help keep the pH of the water lower at around 7.0 pH.

Aquarium soil holds its shape a little better than other types of substrate, and it is used in aquascaping to give the aquarium a natural look while providing a sturdy place for your plants to anchor. The better your plants can anchor into the substrate the better they will withstand even the most active of fish.

For most planted tanks, ADA Aqua Soil is the best aquarium soil. ADA Aqua Soil is recommended for planted aquariums not only for its rich black coloration that allows for your fish and plants to better stand out, but also for its added nutrients that will help your plant grow and thrive. It is an easy substrate to maintain, but like all other substrates, it requires regular maintenance.

Aquarium Substrate Types

While we’ve mentioned some of the best aquarium substrates that are suitable for most, each tank is unique with different needs. Therefore, it is important to fully understand what types of aquarium substrates are available in order to select the best substrate for your specific aquarium.

There are many different types of aquarium substrate, and they each have their benefits. Some may have drawbacks to consider as well.

Different Types of Aquarium Substrate
Different Types of Aquarium Substrate

Aquarium Gravel

Aquarium gravel is one of the most used types of substrate for aquascaping. Not only is it available in different colors and sizes, it is very cost efficient as well. You can find aquarium gravel in just about every pet store, and in many places online. Aquarium gravel can be an inert or active type of substrate depending on what the gravel is made out of. For example, if the aquarium gravel is made of limestone it can affect the pH of the water and make it higher.

Pros of Aquarium Gravel

  • Aquarium gravel allows the water to flow through it which helps prevent the buildup of harmful bacteria.
  • Gravel can provide a stable substrate for aquarium plants to take root in.

Cons of Aquarium Gravel

  • Aquarium gravel can have sharp edges and points that can damage and hurt fish that root through the substrate in search of food.
  • Aquarium gravel has gaps in it that allow for food and debris to fall through. If left unchecked it can cause issues with your water parameters.

Aquarium Sand

Aquarium sand seems fairly straight forward in its description, but there are actually different types of aquarium sand that you can choose from. Aquarium sand comes in a wide range of grain sizes from coarse to fine. It can also come in a variety of different colors which can serve to give your aquarium a pop of color or help your vibrantly colored fish stand out to more easily be seen.

Aquarium sand is an example of an inert substrate as it does not change the pH of the water.

Aquarium Substrate: Coarse Sand
Aquarium Substrate: Coarse Sand

Pros of Aquarium Sand as Substrate

  • Bottom dwelling fish with sensitive barbels, or any fish that routinely dig, root, or scavenge through the substrate, do well with soft sand.
  • Fish waste and food debris remain on the top of sandy substrate, and do not fall down into it. This makes it much easier to clean.
  • Aquarium sand comes in many colors so you can easily find the perfect sand to match your decor.

Cons of Aquarium Sand as Substrate

  • You need to be mindful of where you place the intake of your filter as the sand can become sucked up into the filter and damage it.
  • Aquarium sand is abrasive enough to scratch glass if it manages to get wedged in between your algae scraper, so you will have to be extra mindful when cleaning.
  • Aquarium sand can become densely packed which can trap harmful gasses if disturbed. To prevent this from happening, you will want to poke holes in the aquarium sand to prevent buildup

Aquarium Soil

Aquarium soil is different from the regular soil that you get from outside. It was created especially for aquariums so that the soil does not mix with the water to create a muddy mess. Aquarium soil provides the perfect, nutrient rich environment for aquarium plants to take root and grow. Aquarium soil is an example of an active substrate as it helps keep the pH of the water at a 7.0 and less acidic than it would be with an inert substrate.

Pros of Aquarium Soil as Substrate

  • Aquarium soil is a much sturdier choice for aquascaping as it is easier to form to the shape that you want.
  • Aquarium soil works well for aquarium plants to take root in, as well as helps provide your aquarium with a natural look.
  • Aquarium soil is a great choice if you are wanting a filterless tank as the soil helps break down the waste and debris left behind from your fish.

Cons of Aquarium Soil as Substrate

  • Aquarium soil that is disturbed too much during cleaning or from your active fish will quickly cloud up the water.
  • Most aquarium owners who choose soil will also choose another layer of substrate to go over top of it to help prevent the soil from clouding up the water.
  • Soil should be carefully chosen to avoid it from contaminating your aquarium. It is not advisable to get your soil from outside.

Aquarium Pebbles

Aquarium pebbles are the largest type of substrate used in aquascaping. Like other types of aquarium substrate, pebbles come in different shapes and colorations. Aquarium pebbles are another example of a type of inert substrate as they do not change the pH of the water.

Pros of Aquarium Pebbles as Substrate

  • Aquarium pebbles can be a good choice of substrate, or used as an added layer on top of the substrate.
  • There are many different shapes and sizes of aquarium pebbles as well as different colorations. These can be used to decorate your aquarium and give it an added pop of color that can help your fish stand out and be easier to spot against the background.

Cons of Aquarium Pebbles as Substrate

  • Larger aquarium pebbles have gaps in them as they overlay that fish waste and debris will fall into. This will cause your water quality to decline.
  • Aquarium pebbles need to be cleaned, and the water parameters checked more often to prevent water quality decline from happening.

Crushed Coral

Crushed coral can be a great choice as an aquarium substrate. Not only does it help keep the aquarium more clean by trapping in fish waste and debris, it also helps raise the pH level of the water and maintain its acidity.

Pros of Crushed Coral as Substrate

  • Crushed coral is a good substrate for trapping in debris and keeping the water clean.
  • Crushed coral can help raise the acidity of the pH of the water. This is good for freshwater aquariums, but not so much for saltwater ones.
  • Crushed coral can add a natural beauty to your aquarium.

Cons of Crushed Coral as Substrate

  • Crushed coral is not a good substrate to plant aquarium plants in as it releases too high of a pH which is not good for your plants.
  • Crushed coral will dissolve over time.

Clay Substrate

Clay substrate for your aquarium is a type of inert substrate. This means that it does not affect the pH of the soil. Clay substrate can be used with soil, or mixed in with other types of substrate to add a boost to your plants.

Pros of Clay as Substrate

  • Clay can give your aquarium plants an added boost of minerals that will help them grow.
  • Red clay can add a natural boost of manganese and iron for your plants.
  • Clay is often used as a mix-in with other types of substrate.
  • Clay, much like sand, does not have any gaps in it, so waste and debris left behind from your fish will not fall down into the substrate making it much easier to spot and clean.

Cons of Clay as Substrate

  • Clay substrate can become densely packed, and can suffocate roots if it is not monitored. You can help prevent this by poking holes in the soil to help with the aeration and to prevent any harmful gasses from building up.

Lava Rock Substrate

Lava rock is a type of inert aquarium substrate, which means that it will not affect the pH of the water. Like other types of inert substrate, lava rocks come in different color variations, and is a great inexpensive option for the right setup. Lava rocks are a popular choice for decor as well as substrate for a more natural look.

Pros of Lava Rock as Substrate

  • Lava rocks are porous and provide a lot of surface area for beneficial bacteria to grow.
  • The beneficial bacteria help to keep the water more clean, and thus helps keep the water parameters at more consistent levels.
  • Larger pieces of lava rock can also be used as decor to create caves or other hiding places for fish to destress.
  • They help create a more natural look to your aquarium.

Cons of Lava Rock as Substrate

  • Lava rock can be tough for fish that spend a lot of their time at the bottom of the aquarium. It is possible that an overzealous eater can damage their mouths when going after their food too aggressively.
  • Lava rocks require a lot more cleaning and maintenance. This heavy maintenance starts shortly after purchase as lava rocks have to be prepped and cleaned before they can be put inside an aquarium.
  • You will have to monitor your aquarium water parameters closely as the porous lava rocks can become clogged with debris.

How Much Aquarium Substrate Do I Need?

When figuring out how much substrate you need for your aquarium, you can generally follow the rule of 1 pound of substrate per 1 gallon of water, or at least 3 inches of substrate. By following this rule, you are giving your plants plenty of room to anchor themselves and root into the substrate. Allowing your plants with enough space to anchor into the substrate, you are helping them survive against even the most active fish.

How Do I Change Aquarium Substrates?

There is no standard on how often you need to change your aquarium’s substrate, but one this is agreed upon, and it is that your aquarium substrate will need changing at some point. It is important to check your aquarium for visible signs that the substrate needs changed as well as monitoring the water parameters. Water parameters that are off slightly are your first indication that your tank may need to be cleaned.

Before you get started changing the substrate in your aquarium you will want to make sure that you have gathered everything that you need to get the job done. This will include a separate tank for your fish and plants to go while you are changing the substrate.

Once your fish and plants are safely out of the way, you can begin scooping out the substrate. Make sure that you clean the tank of any debris that might have been left behind. It is also important to make sure that your new substrate has been cleaned before it is added to the aquarium. Brand new substrate could be dirty or have cleaner still on it. Failure to do this important step can harm your fish and plants.

How To Clean Aquarium Substrate

Depending on the type of substrate that you have, there is a certain way to maintain it. If your aquarium is immensely dirty, then you will want to clean a small section at a time to prevent your tank from shock. It is best to choose sections of your aquarium that need cleaning, and work from there only cleaning one section roughly every week or two.

You can use the help of a siphoning tool, or aquarium vacuum for the gravel to help keep the substrate free of debris in between changes.

What Substrate is Easiest to Clean?

All substrates require regular maintenance and cleaning. They all have different ways that they can be cleaned too. If you had to choose a substrate that was a little easier to keep an eye on, sand would be your best bet as you can vacuum off the fish waste and debris from the top as it appears, though this is not a foolproof method for making your substrate last longer in between cleanings.