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How Much Gravel Do I Need for My Aquarium? | Easy way

Adding a substrate is an essential part of decorating your aquarium. Many people choose to decorate their aquarium so that they can have a unique look.

They usually add colorful plants, rocks, seashells, and sand to the tank. For these decorations to be anchored down, you need a significant amount of substrate. How Much Gravel Do I Need for My Aquarium?

Why should You Use Gravel?

How Much Gravel Do I Need for My Aquarium

Gravel is a popular choice of aquarists for use as a substrate. Gravel prevents amoebas and bacteria buildup and is heavy enough not to get pulled into the aquarium filters. Many Fish tank owners think that Gravel looks more natural, mimicking fish’s natural habitats such as the lakes and riverbeds.

And unlike sand, there are larger gaps between gravel particles that help old food and plants sink to the bottom. When old food and plants fall to the bottom, they can rot and decay, making one less hassle cleaning the tank.

What Type of Gavel Should I Choose?

Gravel is available in 3 types, Dolamite, Pea and Regular. Some gravel is finer, and some are coarser. Some fish like coarse Gravel, which they can mess around, and some prefer fine Gravel where they can dig around.

Rooted plants need more refined and deeper Gravel layers, and others will go fine with a regular amount of Gravel in the tank. So, determining which type of Gravel you need depends on the fish and plants you plan to add to the aquarium.

First, figure out what kind of substrate your fish would like to have and then determine the amount of Gravel you add after deciding which plants you will add to your tank.

How Much Gravel for 20 Gallon Tank?

Many aquarium owners consider that 2-inch layer of a substrate as the minimum amount you should put into the tank. To calculate the exact gravel amount needed for a tank, you need your tank’s exact size and dimensions.

You can use an Aquarium Gravel Calculator to solve the amount you need for your tank.

Another easy method of calculating gravel amount is knowing the water amount your tank can hold. A 5-gallon water tank needs about 5 pounds of substrate. So, a 20-gallon tank will require roughly a 20 pound Gravel for the tank.

Can You Put too Much Gravel in a Fish Tank?

Yes. You can put Gravel as much as you like but keep in mind that fish need water to swim on. If you put Gravel to the half of your tank (which you would not), your fish may not have enough water to live. There’s a minimum requirement of gravel amount, but there’s no maximum amount listed anywhere.

More Gravel, the better. However, putting too much Gravel will only eat up your tank’s volume.

How Much Sand Do I Need for a 20 Gallon Long Tank?

You can use sand as your substrate instead of Gravel. The amount you need is the same as gravel amounts. You can use Aquarium gravel calculated above or use the general calculation of one pound of substrate per gallon of water. Generally, you will need 20 pounds of sand for a 20-gallon long tank.

How Many Inches Of Gravel Do I Need For My Aquarium?

Many aquarists recommend at least 2 inches of Gravel for an aquarium. Some fish keepers use a range of 1″ to 2.5″ of Gravel for tanks with no decorations. However, if you want to decorate the aquarium with live plants, you need an additional 1-inch nutrient layer. For the nutrient layer, you can use vermiculite or laterite.

You should cover the nutrient layer with a substrate like Gravel or sand. In some cases, not adding any substrate is a wise choice as it helps you clean the tank quickly. This approach is useful in caring for sick fish in emergency “hospital” tanks.

Is Colored Gravel Bad For Fish?

Colored Gravel can be toxic to your fish if it is colored with cheap dyes. Even high-quality colored Gravel can harm your fish if you don’t wash them thoroughly before adding them to the aquarium.

Gravel has some dust and residue, which can harm or even kill the fish. It is required to wash Gravel (coloured or not) for at least 30 minutes before attaching them to the tank. Some fish doesn’t like bright colors (Ex: Discuss fish) so check with the fish species you have before bringing any bright colored gravel.

How Much Gravel Do I Need For A 55-Gallon Tank

You will need around 60 to 70lb of Gravel for a 55-Gallon tank.

A general rule of thumb goes to 1 to 1 1/2 pound of Gravel per one Gallon.

This amount will make about 2 inches thick layer in your aquarium. If you want to put more than the recommended minimum, that’s fine too. Some fishes and shrimps love to have more substrate.

How Much Gravel For A 75-Gallon Aquarium

If you use the most common Gravel calculation of 1- 1 ½ pound per one Gallon, you will need around 75 to 113 pounds of Gravel for a 75-gallon aquarium. If you plan to use rooted plants in your aquarium, you will have to buy some more Gravel as they need more surface area to colonize.

Should I Use Sand Or Gravel?

Many fish keepers use sand and Gravel as their substrate in their tanks.

Each of them has benefits and drawbacks. While choosing either one is fine, you have to check with your fish’s preferences before choosing one. Some fish, such as cichlids, like sand substrate, eat sand particles to digest their food. On the other hand, Goldfish suffers from intestinal blockages if they accidentally ingest sand.

Gravel substrate allows water to flow through it. It prevents the buildup of amoebas and bacteria in the substrate. Gravel also available in many colors, so you can have a colorful substrate in your aquarium.

Sand doesn’t allow water to flow through, and there are chances of bacteria buildup in the sand. However, if your tank includes fish that burrow and scavenge in the sand, you don’t have to worry much about amoebas and bacteria problem as your fish will do the sand filtering job.

Unlike Gravel, sand has small gaps between particles, preventing old foods and dead plants from going under and rot. Because of that, you can easily clean your tank if you have a sand substrate.

Choosing a substrate is up to you. Sand or Gravel, either one is fine for an aquarium. But before choosing one, you must check if the substrate is suitable for your fish.

What Kind Of Gravel; Best For Planted Tank

Choosing a Gravel type is tricky when you plan to add live plants to your aquarium. Each plant requires a different kind of Gravel for optimal growth.

Large type plants like Anubias and Swordplants need a minimum of 2-5mm sized Gravel to get a good hold with their roots. If you put substrate with smaller particles, these plants will tend to float away very quickly if disturbed.

Small, carpeting-type plants like HC Cuba need a 1-2mm sized Gravel to root perfectly. Whichever substrate you use, you need to layer Gravel with aquarium soil or a nutrient-rich substrate to provide necessary nutrients for the plants as Gravel doesn’t have them.

How Do You Prepare Gravel For A Fish Tank?

If you plan to put Gravel in your tank, you should wash the Gravel thoroughly to remove dust and imperfections as they can cloud your fish tank water and be toxic for your fish.

At least 30 minutes of washing is required until the water gets clear while washing the Gravel. When you finish washing your Gravel, you need to dechlorinate them for about 20 minutes with a dechlorinating agent.

After all these steps, you can incorporate your Gravel into your tank environment.

How To Put Gravel In An Aquarium

You can use your hands or a shovel to put Gravel in an aquarium. It would be best if you did this gently as you don’t want to scratch or damage the tank. After putting Gravel into the tank’s bottom, use your hands to smooth out the Gravel to get an even layer.

Read more Can I Use Outdoor Gravel Or Rocks In an Aquarium? How To Use Them

How Long Does It Take For Gravel To Settle In A Fish Tank?

It takes around 12 to 24 hours for Gravel to settle in a fish tank if you clean Gravel well. If you didn’t correctly clean Gravel, it would take as much as seven days to clear up the cloudiness and settle.

It would be best if you didn’t put your fish into the tank until your substrate settles in the fish tank.

Factors To Consider When Selecting Aquarium Gravel

You should consider three factors when selecting aquarium Gravel; Particle size, color, and composition.

Particle size

Gravel is available in various sizes, from small to large. Gravel is known as a suitable substrate for all kinds of aquarium life. If you want to use live plants in your aquarium, you may need to choose Gravel’s specific size ideal for your plants. Otherwise, you are free to choose any size of Gravel for your aquarium.


You can buy Gravel in different colors. Just remember some fishes like Discus do not like bright colors. So, you’ll have to choose the colors of your aquarium substrate carefully. And avoid buying low-quality Gravel as they contain a cheap dye that is toxic for your fish.


You can buy various types of Gravel, which is made with different elements.

  1. Live Gravel comes with healthy bacteria and microorganisms, which helps prevent new tank syndrome.
  2. Natural/River Gravel collected from riversides and natural gravel pits. These are chemically inert and provide natural colors to your tank.
  3. Clay Gravel made from clay which is rich in iron and minerals, beneficial for planted aquariums.
  4. Artificial Gravel is made from silica or industrial resin. This Gravel is available in various colors and sizes. Artificial Gravel is chemically inert, but rinsing is required before putting it into the tank.

Read more How To Create A Forest Aquascape? 3 Simple Steps

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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.