How Much Gravel for Fish Tank (Is It Necessary?)

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More often than not, we find new fish keepers wondering, “how much gravel for fish tank?”

It can be challenging to assume the amount since every aquarium is different, which means gravel amounts will differ too. Moreover, the aquarium’s look should be considered when deciding on it. 

But there are many benefits to having the right amount of gravel in the aquarium, which we will discuss in this article. Now, let’s go into further details about this.

Do I Need Gravel In A Fish Tank?

Truth be told, you don’t need gravel in the fish tank, as it is not essential for the working of the aquarium per se. However, it does create an environment conducive to the fish, which is why adding gravel should be a priority.

Why Do I Need Aquarium Gravel Or Substrate?

how much substrate per gallon

Biological Filtration

Gravel creates a home for all the beneficial bacteria that remove waste from the tank. That being said, gravel is not necessary for hosting these bacteria, but a bare tank bottom will mean frequent water changes to ensure the water is filtered, which might be tedious for some. 

Moreover, if you have a lot of fish, changes in water parameters are much more likely. This is where gravel comes into the picture, as it will help create a healthy living space for the life inside. 

Fish Habitat

Gravel creates a more realistic living space for the fish. Additionally, it may help reduce reflections in the water. 

Another interesting benefit is that gravel or substrate makes the tank a safe space to breed in. It creates a conducive environment during the breeding season, similar to what can be found in nature. Apart from that, many fish species eat their offspring, and large pieces of gravel can help avoid that by hiding the eggs and fish babies to keep them safe.

Good For Live Plants

Interestingly, it is not just fish and their babies who benefit from the gravel but also the plants you add to the tank. 

Most people like to add live plants to their aquarium for a better look and to create a better living space for the fish. In such cases, adding substrate to the tank is an excellent idea as it protects the plant roots and provides nutrition. 

How To Choose The Right Aquarium Gravel?

how much aquarium gravel do i need

The Fish

The most crucial factor to consider is the kind of freshwater fish in the tank. Some like to play in the gravel, while some like to dig in. So know what kind of fish is in there before picking a type that’d be suitable for them. 

The Plants

Plants with roots usually need gravel in the bottom of the tank, as it provides them with a stable base. Since these plants are top-heavy, the gravel keeps them down and prevents them from floating.

Water Chemistry

Depending on the type of gravel you go for, it can harden the water or add nutrients. So, consider the livestock in the tank and the type of water it needs before picking out the gravel.


Let’s not forget the aesthetics as well! Aquariums have always been known to have colorful gravel in the bottom, making them look better. Additionally, if there are a lot of decorations in the aquarium, then you can always use more gravel to tie the look together. 

How Much Gravel Do I Need For My Fish tank?

Since aquariums come in different sizes, the amount of gravel will also differ accordingly. So, let’s look at some different-sized aquariums and their gravel requirements. 

How Much Gravel For A 5-Gallon Tank?

In most circumstances, 5 pounds of gravel should be enough (one pound per gallon) for a 5-gallon tank. However, you can increase it up to 8-pounds per gallon.

How Much Gravel For A 10-Gallon Tank?

If you are only looking to cover the base of the tank with a thin layer of gravel, 13 pounds should be enough for a 10-gallon tank.

How Much Gravel For A 20-Gallon Tank?

This is the most common aquarium size that people purchase. You can either buy a long 20-gallon tank or a high one. Since the former is longer in width, around 23 pounds of gravel is ideal. For the higher ones, just 19 pounds will suffice.

How Much Gravel For A 55-Gallon Tank?

The 55-gallon tanks are pretty popular since they don’t take up a lot of space but provide ample volume. These aquariums usually require at least 37 pounds of gravel, which can go up to 74 pounds depending on the number of fish and plants in them.

How Much Gravel For A 75-Gallon Aquarium?

Since 75-gallon aquariums are the biggest ones, their gravel requirement is also more. For a thin layer of gravel, 56 pounds should be enough. However, for a dense layer, you will need at least 112 pounds.


Can You Use Garden Gravel In A Fish Tank?

It is possible but not ideal. Outdoor/garden gravel may alter the parameter of the water for the worse. This is why it’s better to use aquarium gravel or substrate that’s meant for, well, aquariums..

Can You Have A Fish Tank Without Gravel?

Bare bottom aquariums are common among people who don’t want substrates to harm the water. Again, it will depend on the fish and the water chemistry the tank needs to maintain. 

Can You Put Gravel In A Fish Tank After Water?

You can, but it will make the setup process difficult. Some gravel pieces might end up floating instead, which is why it’s easier to arrange the gravel first and then add water.

Final Thoughts 

On that note, we come to the end of this guide on gravel in aquariums. We hope this has been informative and will help you when the time comes. 

But before leaving, we would like to offer some advice: adding gravel is not the answer to every problem. Ensure the tank is cleaned at regular intervals and check the food and waste accumulation between the gravel. 

And now, we shall sign off. See you very soon with more such informative content. 

Until next time!

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Jeff Colt

Jeff Colt

Hello, I'm Jeff- an aquarium enthusiast with over 25 years of experience caring for a wide array of tropical fish, including koi, goldfish bettas, cichlids and more! For me: Aquariums are like jello - there's always room for more!

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