How Much Gravel for Aquarium

The majority of fish tanks use gravel at the bottom of the tanks to make it look nicer and to act as an anchor for the other ornaments and plants. It also catches bits of fallen food that the fish can then peck at a later date. The gravel can be made up of rocks, shells, or sand. 

Aquarium Soil is also sometimes used for the gravel in aquariums and this allows the owner to plant live aquarium plants into it. This offers some much-needed greenery into many fish tanks. 

Setting up an aquarium can be more difficult than you first think, and more expensive. So, you might be wondering how much gravel do you really need in your aquarium, and what are the factors affecting the decision. 

We’re going to be answering both of these questions today, so you know exactly how much gravel you’ll need to fill your tank with. 

How Much Gravel Do You Need?

A good starting point is to consider it like this - you need two inches of gravel for an aquarium. This is the minimum amount of gravel you should use and you can definitely opt for more if you’d like to. 

If you know your tank’s dimensions then you’ll be able to work out how much gravel you need. For example, if your tank was 20 x 10 inches, you’d need around 27 pounds of gravel for a two-inch bed. 

You might be screaming: but how do you find out how much gravel covers one square inch of the tank? Well, we cannot help you there. However, there are some very handy aquarium gravel calculators online to use. 

Once you’ve used the handy calculator, you’ll easily be able to find out how much gravel you’ll need for your tank. However, there are still some pressing factors to consider before purchasing that amount of gravel. Let’s discuss these to get a more accurate estimate. 

Factors Affecting the Amount of Gravel you Need

Type of gravel

The type of gravel you want to use will determine how much you need. For example, chunky rock gravel will sit on top of each other creating lots of holes for air and water to flow through. This means that the gravel will sit much higher than tightly-packed gravel, making the need for more of it obsolete. 

On the other hand; however, using gravel such as sand or aquatic soil will often require more. This is because the water pressure pushes the fine particles down into all of these aeration holes. As the sand packs tightly together, the height of the gravel will decrease meaning that you need more of it to reach at least two inches. 

So, the type of gravel that you’re planning on using will greatly affect how much you need to fill the aquarium. Luckily, the calculator that we mentioned earlier allows you to opt for different types of gravel, giving you accurate measurements of how much of each that you’ll need. 


The type of gravel you choose doesn’t just depend on your personal preference, unfortunately. There are plenty of reasons why you’d choose different types of gravel to use, one being the fish that you keep in the tank. 

This is perhaps the most important factor to consider when choosing the gravel you use as the fish have to live with it every day. Some breeds of fish prefer fine gravel, such as sand or soil, to dig into, while others enjoy throwing rocks around. Have you ever seen a fish spit a rock at another? It’s amazing. 

Once you determine which fish you’re going to be keeping in your tank you can then determine what gravel to use and therefore how much of it you’ll need. 

Decorative ornaments

Ornaments often require gravel to anchor them down so that the fish don’t go knocking them down. Depending on the ornaments, you’ll need more gravel to weigh them down. For example, if a heavy ornament needs to be anchored with gravel, the gravel will need to be heavy enough to hold it. 

If lightweight gravel such as sand is being used, you’ll need more of it to generate enough weight to keep it stable. On the other hand, you might need less gravel to anchor the ornament if you are using heavier gravel such as rocks. So, make sure that you know how many ornaments you’ll be putting into your tank to help you figure out how much gravel you’ll need. 

Some aquarium hobbyists prefer to fill their tanks to the brim with heavy ornaments, while others like to keep it simple with lots of greenery. Fake plant ornaments are not as heavy as ceramic ornaments so you won’t need as much gravel for these decorations. 

Live Plants

Live plants offer a great addition to any aquarium, so why don’t you implement them into your tank? These types of plants need to be planted into aquarium soil if they have roots, which will affect your decision for your gravel. If the roots are well-established, you’ll need a thicker layer of soil. 

The larger the live plant, the more soil you’ll need to keep it happy. However, if you’re using air plants that don’t have any roots, it doesn’t matter what type of gravel you use because they take their nutrients from the water rather than the gravel. Therefore, for air plants at least, the amount of gravel you need does not concern the live plants.


Overall, there is not a set amount of gravel that you need to fill a tank because aquariums come in all shapes and sizes imaginable. Using an online calculator can help you to determine how much gravel you should look for, but this is only an estimate. 

The amount of gravel you’ll need will depend on the type of gravel you’re using, and some factors affect this as well. Consider the fish you’ll be keeping and research what they enjoy the most. The type of decorations you use will also determine how much gravel you should get, so leave no stone unturned!