Best Substrate for Goldfish (Sand, Gravel, Marbles)

Goldfish don’t need substrate for their survival.

However, fish tank owners usually add sand or gravel substrates. Some of them even keep a bare-bottom fish tank.

While goldfish may not need a substrate to survive, having it does have some benefits.

Of all the different options, pea gravel is the best substrate for your goldfish (but there are more options as well).

In this article, we will learn about the best substrates you can use for Goldfish.

Benefits of Having Substrate in Your Fish Tank

Substrates can offer a number of benefits to your goldfish tank. They can help to keep the water clean by providing a place for beneficial bacteria to grow.

This bacterium breaks down waste products in the water, helping to keep ammonia and nitrite levels low.

Substrates can also help to promote plant growth by providing nutrients and anchor points for roots.

In addition, substrates can make your aquarium look more natural and attractive.

Is Substrate Necessary for Goldfish?

While the substrate is not necessary for goldfish, it can provide a natural environment for them to swim in.

Goldfish that live in tanks with substrate tend to be healthier and have fewer health problems.

If you choose to add substrate to your tank, be sure to select one that is safe for goldfish and easy to clean.

Best Types of Substrates for Goldfish

There are many different types of substrates available for goldfish tanks.

The most common types are sand, gravel, and pea gravel.

Gravel Substrate

Gravel is a popular choice for goldfish tanks because it comes in a variety of colors and can be used to create interesting aquascapes.

It is great for those who are beginners in keeping goldfish.

Gravel is available in a variety of sizes, so it’s important to choose one that will suit your goldfish’s needs. Not all types of gravel are suitable for a goldfish tank.

Gravel designed specifically for fish tanks will keep the water safe from toxins and other pollutants.

Furthermore, it doesn’t have any sharp edges; hence your goldfish will not be harmed.

There are some potential hazards of keeping gravel substrate in a goldfish tank. The smaller pebbles may be swallowed by your goldfish, causing them to choke.

You can prevent this from happening by keeping the gravel that is bigger than the pea-sized pebbles.

The bigger the size, the less likely your goldfish will be able to put them in their mouths.

Pea gravel is a small type of gravel that is often used in the bottom of goldfish tanks for drainage. It is one of the most common gravel substrates that fish owners use for their aquariums.

One benefit of using pea gravel is its ability to facilitate the growth of aquarium plants.

The plant roots can grow between the pebbles without any problem as the space has a lot of aeration.

Moreover, this also prevents any gas pockets that are toxic to be formed. By using just a gravel vacuum, the pea gravel can be cleaned quite easily.

Fish owners need to remember that pea gravel must be packed densely. This will avoid the accumulation of waste into the gaps between them.

Overall, gravel is among the leading choices for substrate in fish tank owners. It helps in cleaning the tank base and provides a good foundation for aquarium plants too.

Sand Substrate

Sand is a good choice for goldfish tanks because it is easy to keep clean and provides a natural look.

Goldfish are known to dig in the sand, so it’s important to choose the type that won’t be easily displaced.  

Not all sand is ideal for fish tanks. Fish owners should be careful of using only aquarium sand as it is specially designed for fish tanks.

Aquarium sand has a very soft feel to it as it has been sieved and filtered repeatedly.

Aquarium sand is available in different colors to help improve the visual appeal of the fish tank.

Since goldfish are freshwater fish, you need to use the sand that is exclusively used for freshwater fish.

Otherwise, your goldfish may be disturbed a lot or may have difficulty adjusting to their fish tank.

If you have marine fish with your goldfish, they will need a different type of sand substrate. This particular type has salt and bacteria that are suitable for marine fish but not goldfish.

Aquarium sand for freshwater fish is available in many colors, which can add a lot of vibrancy to your fish tank. Fish owners can choose to mix all the colors or layer them as they see fit.

There isn’t a definite answer to whether sand is suitable for your goldfish or not, as opinions are divided. Some people say the sand substrate can cause irritation to the goldfish’s gills.

Other people disregard this to be a baseless statement. They are of the opinion that goldfish can live perfectly well in a fish tank with sand substrate.

Play Sand

Play sand is another type of substrate that can be used in goldfish tanks. Play sand is a type of sand that is specifically designed for use in children’s playgrounds.

It is very fine-grained and soft, making it safe for goldfish to swim in. Play sand is a good option for goldfish tanks because it is inexpensive and easy to find.

Play sand doesn’t come in multiple colors, unlike regular aquarium sand. While it may not add to the visual appeal, it does provide a very natural look for your fish tank.

Goldfish are known to particularly enjoy digging in the play sand. Often goldfish consume small quantities of sand, which may even help facilitate their digestion process.

It is extremely easy to clean play sand, and it also improves the water quality. With a play sand substrate, the waste rests on the surface and you can vacuum it up easily.

Another benefit of having play sand is that it creates sand beds. Sand beds are formed when there are anaerobic bacteria pockets developing in the substrate.

This bacterium is extremely useful for providing much of the required nutrients to the aquarium plants.

The sand beds also remove nitrates from the water, which are harmful for the goldfish.


Marbles can also be used as a substrate, but they are not as popular because they can be difficult to keep clean.

Marbles are mostly used for decorative purposes, and there is no significant benefit for the goldfish.

Marbles are perhaps the least favorable choice for goldfish substrate.

Not only do marbles trap lots of waste, but they are also quite expensive. Goldfish may even swallow marbles which will cause them to choke.

Marbles also aren’t a good choice if you want to keep aquarium plants. Overall, they should be avoided if you have goldfish in your fish tank.

Also read: How to Clean Fish Aquarium Rocks?

Bare Bottom

Some goldfish keepers choose to keep their tanks bare-bottomed, without any substrate at all.

This is a good choice if you have a particularly messy goldfish or if you want to make cleaning the tank easier.

However, bare bottom tanks can look sterile and unattractive. If you do choose to keep a bare bottom tank, be sure to provide plenty of hiding places and decorations for your goldfish.

One benefit of bare bottom fish tanks is that the water quality will remain high for a long time. Since there won’t be any waste trapped in the substrate, the water can be cleaned very easily.

Bare bottom fish tanks also have less chances of goldfish being injured or being choked. However, keeping live plants will become almost impossible.

Fish owners who still want to keep plants in their bare bottom aquariums use small jars and pots with live plants in them. However, they need to make sure those jars and pots aren’t knocked over.

What to Consider When Selecting Substrate

There are many different types of substrates available, so it’s important to choose one that will suit your goldfish’s needs. Some factors to consider include

Size of the Substrate

Smaller goldfish may be able to swim through larger particles of the substrate, so it’s important to choose a size that they won’t be able to swallow.

Substrates that have large particles can trap uneaten food and other waste. This accumulation will lower the water quality if they aren’t removed immediately.

On the other hand, tiny substrate particles may compact together and create spaces with less oxygen.

These pockets can produce sulfide, which is highly dangerous for all types of fish, including goldfish.

Texture of the Substrate

Some goldfish breeds, such as fancy goldfish, have long fins that can get tangled in coarse substrates.

If you have a Goldfish breed with long fins, you’ll need to choose a finer substrate.

Goldfish are naturally curious fish, and they like to dig in the substrate for any leftover food.

A sandy substrate, for example, can be dug easily, while a rocky substrate will not.


A substrate can immediately improve or lower the attractiveness of your fish tank based on what color you have gone for.

However, choosing the right color is merely a matter of personal choice.

Some fish owners love having a substrate of bright colors. Others would prefer having a more natural look.

Fish owners often report that having a dark-colored substrate makes their fish tank more crowded.

A light-colored one, on the other hand, makes the tank light and open.

Plants in Your Fish Tank

If you have live plants in your aquarium, you’ll need to choose a substrate that will suit their needs.

You’ll also need to consider whether you want a substrate that can be used for planted tanks or one that is specifically designed for goldfish tanks.

This is because fish tanks specific for goldfish have freshwater requirements. These will vary from other tanks that are for saltwater creatures.

Also read: 20 Best Plants for Goldfish Tank (with Images)


Substrates can range in price from very affordable to quite expensive. It’s important to choose a substrate that fits your budget.

Marble substrate is quite expensive, but the sandy ones are commonly available and very cheap.

How to Add Substrates in Your Goldfish Tank

Adding substrate to your goldfish tank is relatively simple. You will have to wash the substrate in water to remove any dust or debris.

Next, spread an even layer of the substrate over the bottom of the tank.

Finally, add the appropriate amount of water to the tank and let it cycle for a few weeks before adding goldfish.

When to Change Your Substrate

You may need to change your substrate if it becomes too dirty or if you want to add new goldfish to your tank.

It’s a good idea to replace the substrate in your tank every few years to ensure that it stays clean and suitable for the goldfish.

Also read: How To Clean Fish Tank Gravel Without A Vacuum?

How Can I Make Sure My Substrate Is Safe for Goldfish?

When selecting a substrate for your goldfish tank, be sure to choose one that is safe for goldfish.

Gravel and sand can trap debris and waste, which can then release harmful toxins into the water.

Pea gravel is less likely to trap debris and waste, making it a safer choice for goldfish tanks.

It’s also important to regularly vacuum the substrate to remove any build-up of debris and waste.

Frequently Asked Questions – FAQs

Which substrate is best for goldfish?

Since goldfish don’t need substrate for survival, there is no best answer.

However, there are many substrates that are good for them, like gravel and sand. Bare bottom tanks are also good for them.

Are substrates expensive?

It depends on the type of substrate you are going for. For example, play sand is not expensive at all, but marble substrate is.


Goldfish can be perfectly happy in a substrate-free environment as they don’t need it for their survival. However, they will definitely love having one.

Many types of substrates are good for your goldfish. Since they like to dig around, the sand substrate will be a good choice for them.

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