Fish Tank Gravel Calculator

Fish Tank

Tank Type - (Rectangle)Tank Type - (Hexagon)Tank Type - (Cylinder) Length: 24 in. Width: 12 in.

Gravel

Gravel Type - (Pea Gravel)Gravel Type - (Regular Gravel)Gravel Type - (Dolomite Gravel) Weight: 37 lbs. Depth: 2 in.

Aquarium Gravel Depth

One of the first things you will have to consider when setting up a new fish tank is how much gravel you will need to add. The amount of gravel you will need depends on the look you are trying to achieve, and the kinds of fish and plants you plan on adding to your tank.  If you want to know how much gravel you will need for your tank, use the fish tank gravel calculator located above to find the answer.

For most purposes, a gravel depth of 2 inches is sufficient for most fish tank setups. If you don’t plan on putting live plants in your tank you can get away with 1 inch of gravel or even less in some situations.

Planted Tanks

Planted tanks require a minimum of 2 inches of gravel in order for the plants to build a healthy root system. Larger plants with more extensive root systems will require more substrate than smaller less deeply rooted species.

The type of gravel you choose for a planted tank is also another point to consider. Smaller gravel like pea gravel is more suitable for a planted tank since it gives the plants roots more area to colonize. Larger gravel, on the other hand, won’t give the plants enough surface area for its roots to hold onto, which can lead to poor nutrient absorption and sick poorly rooted plants.

If you plan on adding deep-rooted plants like sword plants then it is advisable to have a tank with a gravel depth of at least 4 inches. Larger heavy feeding plants may also require an added nutrient base under the gravel like fluorite aquarium substrate to reach their full potential. Any additional nutritive substrate should be taken into account when calculating the amount of gravel you will need to fill your tank.

Some plants like anacharis have little to no root system since they pull their nutrients straight from the water, so they only really need the gravel to hold them in place. For plants with minimal root systems, all you will need to do is sink their crowns deep enough in the gravel so they don’t float away.

Unplanted Tanks

The minimum recommended gravel depth for an unplanted tank is 1 inch. The amount and type of gravel you add to an unplanted tank really comes down to how you want the fish tank to look when it is fully decorated. In some unplanted fish tanks, gravel might not even be necessary or desired like in a breeder tank, or in a tank where you want to keep the debris and built up waste to a minimum.

The only time an unplanted tank will need to have a deeper gravel bed is if you plan on using an undergravel filter. In that case, your tank will need to have a gravel depth of at least 2 inches for the under gravel filter to work properly. The reason for this is that the gravel acts as the filter media when you use an undergravel filter in your tank. In order to remove ammonia, nitrites, and debris from the tank you need to have more gravel to increase the amount of surface area for the bacteria to colonize and for the debris to get trapped in.

If you don’t plan on using an undergravel filter then the depth of the gravel in your fish tank is only dependent on your personal preference. Some people like the look of an aquarium with a deep substrate even in an unplanted tank. While others prefer to add just enough gravel to cover the bottom of the tank so it is just deep enough that there is no glass or acrylic showing.

Most decorations will work well on a shallow substrate since they usually have smooth flat bases that won’t damage a tank. Large rocks, on the other hand, can have sharp edges that can crack or scratch a tank. If you plan on adding large rocks to your tank then having a deeper aquarium substrate can help protect the bottom of your tank from inadvertent scratches or cracks.

How Much Gravel for a 10 Gallon Tank

Choosing the right amount of gravel for a 10 gallon tank is relatively easy once you know the tanks dimensions. Most ten gallon rectangular tanks are 20 inches long and 10 inches wide. Which means the surface area of the bottom of a ten-gallon tank is 200 square inches.

In order to cover 200 square inches with one inch of gravel, you will need a minimum of 13 pounds of gravel. If you prefer to have a two-inch gravel layer in a 10-gallon tank then you will need 26 lbs of gravel.

A ten-gallon tank is a relatively small tank, therefore, you might want to stick with one inch of gravel. This will allow your fish to have more room to swim around in, and it will increase the volume of water you can add to the tank. If on the other hand, you plan on adding live plants with a deep root system, then you should go with 2 inches of gravel even if it takes away a little tank space.

How Much Gravel for a 75 Gallon Aquarium

There is a lot of ground to cover in a 75-gallon aquarium when it comes time to add the gravel. Most 75 gallon aquariums are 48 inches long and 18 inches wide. With a total surface area on the bottom of the tank of 864 square inches.

To cover 864 square inches with one inch of gravel you will need at least 56 pounds of gravel to do the job. If you want to have a 2-inch layer of gravel you will need a minimum of 112 pounds of gravel to get a layer that thick.

In most cases, a 2-inch layer of gravel will look rather thin in a 75-gallon tank. Most people with large tanks prefer to have a substrate layer that is 3-4 inches deep to fill out the tank. Which means you may need upwards of 224 pounds of gravel to get the look you desire in a 75 gallon aquarium.

How Much Substrate for a 20 Gallon Tank

One of the most common aquariums in the fish keeping hobby is the 20 gallon tank. Since it is such a popular tank volume it comes in both long and high configurations. The long and high 20 gallon tanks have different dimensions, so we will address them separately so you can get a better idea of how much substrate they each need.

20 Gallon Long Tank

The 20 gallon long aquarium takes up more floor space which means it will require more gravel than a 20 gallon high tank. A 20 gallon long tank measures in at 30 inches long and 12 inches wide. Therefore a 20 gallon long tank has a surface area of 360 square inches on the bottom of the tank.

If you want to cover 360 square inches with one inch of substrate you will need 23 pounds of gravel. To add a 2 inch layer of substrate you will need 47 pounds of gravel to achieve that depth.

20 Gallon High Tank

The 20 gallon high aquarium has a smaller overall footprint, and for that reason it is the more economical tank to buy gravel for. The most common size of a 20 gallon high tank is 24 inches long and 12 inches wide. That means the surface area at the bottom of the tank is 288 square inches, which is 72 square inches less than a 20 gallon long tank.

To cover 288 square inches with one inch of gravel you will need 19 pounds of gravel. In order to have a 2 inch substrate layer, you will need 37 pounds of gravel. As you can see you can get away with a lot less gravel in a 20 gallon high tank versus a 20 gallon long tank for any given depth of gravel you may require.

How Much Gravel for a 55 Gallon Tank

A 55 gallon tank is one of the more popular entry-level large aquariums on the market since it provides a large volume without taking up a lot of floor space. A 55 gallon tank usually measures in at 48 inches long and 12 inches wide. Therefore the bottom of a 55 gallon tank has a surface area of 576 square inches.

If you want to cover 576 square inches with 1 inch of gravel you will need 37 pounds of gravel. To cover that same area with 2 inches of gravel you will need 74 pounds of gravel in order to fully cover that same amount of space.

Like most other large aquariums a 55 gallon tank may require a deeper gravel bed to have a filled out look. Also if you plan on adding large live plants to a 55 gallon aquarium then you might want to add 3-4 inches of gravel to ensure your plants thrive in your tank. If you plan on adding a 4 inch bed of gravel just be aware it will take 150 pounds of gravel to achieve that gravel depth.

How Much Gravel for a 5 Gallon Tank

A 5 gallon tank is a small tank that won’t require much gravel when it comes time to get it up and running. Most 5 gallon tanks on the market measure in at 16 inches long and 8 inches wide. Which means they have a relatively small footprint of 128 square inches.

In order to cover 128 square inches with 1 inch of gravel, you will only need 8 pounds of gravel. If you prefer to have a gravel depth of 2 inches then you will need 17 pounds of gravel.

In most cases, a 1 inch layer of gravel is more than enough for a 5 gallon tank. Adding more gravel will only reduce the living space for your fish. The gravel will also displace more water which means there will be less water to buffer against poor water conditions.

The only reason you should consider a deeper substrate layer in a 5 gallon tank is if you plan on adding live plants. In that case, you should really only be adding small plants with a shallow root system which means you could still get away with a shallower gravel depth.