Aquarium Sand Vs Gravel: Which Substrate To Choose

One of the first decisions you will face when designing an aquarium is what type of substrate to use at the bottom of your tank.

This is more than just an aesthetic choice; it also affects the setup and longevity of your aquarium. Gravel is a popular choice for freshwater aquariums, but sandy substrates may be a better choice in specific situations.

Here’s everything you need to consider when choosing between aquarium sand or gravel!


Sand Gravel
– Prevents dirt from sinking into the substrate
– Ideal for delicate fish such as shrimp and loach.
– Ideal substrate for most aquatic species
– Works with all types of filtration systems.
– Hides visible debris better than sand

I remember setting up my first aquarium as a child. It was nothing fancier than a feeder bowl of goldfish and African dwarf frogs. There weren’t many commercial substrate options in the 1980s, so it’s probably no wonder my 8-year-old leaned toward bright blue and green gravel bags.

These days we’re not limited to pea-sized bags of gravel in the colors of the rainbow. You can create just about any effect you want in your tank by choosing the right substrate. The material you choose affects your aquarium setup and whether your fish, invertebrate, and/or plant community thrives or struggles.

While there are a variety of options for the bottom of your tank, including using potting soil, peat moss, or even leaving it bare, most aquarists opt for a gravel or sand bottom.

What are the differences between sand and gravel aquariums, and how do you decide on the best substrate for your tank?


If you are looking to recreate the smooth, calm appearance of a river or lake bottom, then aquarium sand could be your substrate of choice! Sand is an attractive and cost-effective option for the bottom of freshwater aquariums.

Sand comes in a variety of shades and colors and can be extremely fine or almost as coarse as gravel. Natural sand is made up of small pieces of shells, rocks and/or organic materials with a diameter of 1/16 to 2 mm.

Aquarium sand is usually made from crushed quartz, coral, or minerals such as aragonite, or is artificially manufactured from a silica base. Unlike natural sand, aquarium sand is uniform in size and shape and has no sharp edges that can harm aquatic organisms.

Commercial products may be labeled as natural or river sand and look similar to the sand you see along a boardwalk. However, unlike sand straight from the river, these bags of substrate have been processed and cleaned.


There is no formal way to categorize sand other than by particle size. If a substrate is between 1/16 and 2 mm in diameter, it is called sand regardless of its composition.

This can be confusing when looking for a suitable aquarium substrate. Sand is used in many industries, from construction to manufacturing. Many sand products are not safe to use in an aquarium or are particularly unsuitable for freshwater tanks.

Here is a list of the types of aquarium sand you will find and some notes on the benefits and drawbacks of each type:

  • Live Sand – Described as “live” because they contain naturally occurring aquatic bacteria and other microorganisms, these bags come filled with fresh or salt water as well as substrate.
  • May prevent “new tank syndrome” because bacteria break down waste products and keep water chemistry stable
  • No rinsing required before adding to your tank
  • It is usually more expensive than other options.
  • It may not be suitable for freshwater community tanks, but some products work well for African cichlids and other aquatic species that prefer high water pH.
  • Product recommendation: Pure Water Pebbles Bio Activ Live African Cichlid Sand
  • It comes in a wide variety of natural shades to match your tank decor.
  • Most products are safe for use in freshwater aquariums and do not alter the chemistry of the water.
  • Not specifically designed for aquariums and can cloud water or clog filters even when rinsed
  • Product recommendation: Exo Terra Riverbed Sand
  • Sand Plant – Not really sand, as these products are usually made from clay containing iron ground into small sand-sized particles.
    • It provides plants with the nutrients they need to thrive.
    • The porous clay particles allow water to flow through and healthy bacteria to flourish in your substrate.
    • Chemically inert and will not alter the chemistry of the water.
    • Available in a limited number of colors.
    • Product recommendation: black sand Flourite
  • Pool Sand – Used in filtration systems, pool sand is a pale-colored, natural product that has been cleaned and sifted to a uniform size.
  • Inexpensive and easy to buy in large quantities.
  • Heavier than play sand and less likely to cloud aquarium water and clog filters.
  • Chemically inert and will not alter the chemistry of the water.
  • Not ideal for most planted tanks.
  • Limited range of shades and colors.
  • Play/Artificial Sand – Made with silica, play sand comes in a wide variety of bright colors and natural shades.
    • Inexpensive and easy to buy in large quantities.
    • Usually coated to prevent color from bleeding
    • Chemically inert and will not alter the chemistry of the water.
    • Lighter than pool sand and can clog filtration systems.
    • Not ideal for planted tanks


The main benefit of using a sand substrate in your freshwater aquarium is the smooth, natural appearance. I myself am a big fan of the sandy bottom look.

The sand also prevents debris and waste products from sinking into the substrate. Instead, they remain in the top layer of sand where they can be grabbed and removed by the filter inlet. You can also carefully vacuum up debris with a hose.

Sand is a desirable substrate in tanks housing freshwater invertebrates, cichlids, or burrowing fish such as Kuhli loaches.


Sand is not the ideal substrate for all tanks and does impose some limitations when used in freshwater aquariums.

The small diameter of the sand grains prevents water from flowing through its substrate. This creates dead zones in your tank; areas where all oxygen has been depleted. Having proper filtration and ample water circulation in your tank will help prevent these zones from developing.

The sand also prevents the roots of the plant from absorbing vital nutrients, as it prevents water from flowing through the substrate.

If you are planning a planted tank, then sand may be something to avoid. Many aquatic plants have shallow roots and do not thrive when planted in sand. You can mitigate these issues by using a substrate designed specifically for planted tanks.


Sandy substrates can present challenges to cleaning and maintaining your tank. Since debris collects on top of the substrate, sandy bottoms often look dirtier than gravel tanks.

Sand is also very dusty and difficult to rinse off, and the particles are so small and light that they can be easily sucked up by the filtration system or vacuum hose. Sand also doesn’t work with undergravel filters.

You may need to adjust the inlet on your hanging or canister filter to prevent them from clogging with sand. It may also take a few days and a few rounds of water changes before your tank is clean after adding sand.


Sand is an ideal substrate for animals such as:

Many aquatic plants struggle in sandy substrates, but these species thrive:


Gravel is the most common type of aquarium substrate and is an ideal product for most freshwater aquariums. When you opt for a gravel bottom, you’ll have a wide variety of options in size, color, and composition.

Gravel is usually made from rocks such as quartz or sandstone that have been crushed, smoothed, and rounded. Gravel can be almost as fine as sand or appear as a collection of pebbles at the bottom of your tank.

Artificial aquarium gravel can be coated with a brightly colored stain or paint and sealed to prevent color flaking.

Other types of gravel are porous and allow bacteria and microorganisms to thrive in their substrate. The presence of this bacteria helps stimulate the nitrogen cycle and converts toxic waste products into a safer form.


As with sand, there is no formal definition for aquarium gravel. Gravel generally ranges from just over 2mm to ¼ inch in diameter, which is about the size of a dry pea.

While you can purchase bulk gravel from construction supply companies, these types are generally not safe to use in aquariums. They can be contaminated with toxins or heavy metals and can poison your tank. Stick to products made especially for aquariums for the best results.

Here are the most common types of aquarium gravel and the benefits and drawbacks of each type:

  • Live Gravel – Similar to live sand, these products are packed in fresh water and contain bacteria and microorganisms along with their substrate.
    • Helps prevent new tank syndrome
    • May contain nutrients to help planted tanks thrive
    • No rinsing required before adding to your tank
    • Suitable for most freshwater species.
    • It is usually more expensive than other options.
    • Limited range of sizes and colors
    • Product recommendation: CaribSea Eco Complete Planted Black Aquarium Sand
  • Natural/River Gravel – As the name implies, these products are collected from riverbanks and mined from gravel pits. They are cleaned and processed to approximately uniform size and shape. The small pebbles appear smooth but are usually not covered with a sealer.
  • Wide variety of natural colors and textures available
  • Allows water to flow through the substrate, avoiding dead zones.
  • Suitable for most freshwater animals.
  • Chemically inert and will not alter water quality.
  • It allows healthy bacteria to establish themselves throughout your substrate.
  • The porous surface can also encourage blue-green algae blooms which can be difficult to remove.
  • Product recommendation: CNZ Aquarium Natural River Gravel
  • Clay Gravel – Another option for planted freshwater aquariums is to use an iron- and mineral-rich substrate made from clay.
  • Provides aquatic plants with the nutrients they need to thrive.
  • It allows water to circulate and healthy bacteria to flourish in the substrate, preventing dead zones.
  • Suitable for most freshwater organisms.
  • Clay is chemically stable and will not alter the chemistry of the water.
  • More expensive than many other options
  • Often very dusty and requires a lot of rinsing before adding to tank.
  • Porous surface can allow blue-green algae blooms
  • Product recommendation: Flourite Black Clay Gravel
  • Artificial Gravel: These products are typically made from silica or an industrial resin. They can also be made of natural gravel covered with an acrylic coating.
  • Variety of colors and sizes to suit all preferences, including glow-in-the-dark and gravel that glows under a black light.
  • Suitable for most freshwater animals.
  • Little rinsing required before adding to tank
  • Chemically inert and does not alter the chemistry of the water.
  • Smooth surface is not ideal for establishment of healthy bacteria
  • Colors may fade or flake over time
  • Product Recommendation: Nature’s Ocean Aquarium Gravel Blackberry Glo


Gravel is popular with freshwater aquarists for a number of reasons.

It is ideal for rearing almost all freshwater fish and most invertebrates. Some of the burrowing species prefer sand, but most do well on gravel if they have rocks and things to hide under.

Gravel is also the ideal choice for growing aquatic plants, as it allows the roots to absorb nutrients from the water flowing through the substrate. Even if you don’t opt ​​for a plant-specific medium, it’s easier to keep a gravel tank planted than one with a sandy bottom.

Buried aquariums encourage the growth of colonies of bacteria and other microorganisms that eat ammonia throughout the substrate. This is desirable as they break down waste products and help maintain a healthy ecosystem in your tank.

You will have a wider range of filtering options when you go with a gravel substrate as you can use under gravel or hanging/canister filters with your tank. Gravel will not clog filters or be sucked up when using a vacuum hose. A final reason gravel substrates tend to be more popular in aquariums than sand is because they hide debris better.

Small particles of food and other material that stand out against a sandy bottom can be indistinguishable when at the bottom of a gravel tank.


There are not many drawbacks to using gravel in your freshwater aquarium. It’s an ideal choice for community and planted tanks and lends itself to endless customization.

The main disadvantage is that these substrates also make it difficult to remove toxic blue-green algae if you have an outbreak. Sandy substrates generally limit these shoots to the topsoil, as water cannot flow through the small sand particles.

Conversely, gravel can allow algae to grow throughout the substrate, where it can be difficult to treat. This can be a bigger problem with porous gravel types, but the use of a UV sterilizing filter can help prevent these algal blooms and other problems with waterborne parasites.


It is easier to maintain a gravel tank than a sand tank. You can set the filter intakes quite low because the gravel is too heavy to be sucked into the filter.

When doing water changes, it’s very easy to vacuum up debris without also picking up gravel. Gravel tanks often appear neater and better maintained than their sandy counterparts.


Gravel is the substrate of choice for many beginners and experienced freshwater fish keepers because it is so well suited for raising aquatic animals and plants. There really are no limits to what you can do with a freshwater gravel aquarium.


It is not easy to change your tank substrate once you have established an aquatic community. To avoid problems, choose the substrate that works best for the fish and plants you plan to keep in your dream tank.

If you are still not sure which is the best option for your freshwater aquarium, here is my advice:

Use aquarium sand if:

  • You prefer the gritty look
  • Have a hanging or canister filter
  • You want to keep freshwater fish or invertebrates that like to burrow into the substrate
  • Don’t worry about the «messy» appearance of the debris at the bottom of the tank.
  • Not too concerned about the limitations in the cultivation of aquatic plants.
  • You want to take on the challenges of maintaining a sandy tank environment

Use Gravel if:

  • Do you prefer a neat looking tank or the gravel look
  • You want a thriving or densely planted aquarium
  • have an underground filter
  • You want a wide variety of substrate sizes and colors to choose from
  • You’re not sure which aquatic species you’ll end up with and want to keep your options open
  • Prefers the ease of maintaining a gravel environment

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