How Many Pounds Of Gravel Per Gallon In My Aquarium

Gravel, also known as substrate, is an essential aspect of your freshwater aquarium. When shopping for gravel you want to choose one that is going to support the needs of your fish. Make sure to read the labels and verify that it is produced for the species of fish you have or want to put in your tank. Always purchase gravel that is specifically made for aquariums. Other gravel can harm your fish and alter the pH levels in your aquarium.

But how do you determine how much gravel you should put in your aquarium? The general recommendation is about 2 inches. You can get away with 1 inch in a fish-only tank. But if you have plants, you want to use 1 to 1.5 pounds of gravel per gallon. So, 60-70 pounds of gravel is what you would need for a 55-gallon tank.

Gravel is going to help your fish by maintaining water quality.

There are a wide variety of types/styles of the grave for your aquarium. I am going to cover some of those different types. I will also discuss, more in-depth, some of the aspects in determining which gravel is best for your aquarium.

There are certain factors you need to consider; such as fish, plants, size of the tank, and other decorations.

Gravel for Fish

The fish that you house in your tank is going to aid you in choosing the gravel for your aquarium.

Once you decide on the type of fish you want to have, do a little research to figure out what gravel is going to be the best.

Some fish prefer finer pieces of gravel to dig around in and some prefer courser gravel. Keeping your fish happy is also part of keeping them healthy.

Gravel for Plants

If you choose to have the rubber/plastic plants then it really doesn’t matter what type of gravel you use.

If you are going to use live plants then it is going to depend on if they are rooted or non-rooted. Non-rooted plants will receive their nutrients through the water.

But your rooted plants are going to receive the needed nutrients from the water and the substrate.

If you have plants with bigger roots you are going to need a deep layer of the finer gravel. Smaller plants can survive the courser gravel and shallow levels of it.

You will have to match the plants to the fish so that the gravel you use will benefit both of them.

Aquarium Size and Decorations
The size of your aquarium is the biggest factor in how much gravel you are going to need.
The fish, plants, and other decorations tell you the type of gravel that you will need to use.
If you have larger decorations, you are going to want to use more gravel. It is going to make your aquarium more appealing than having a thin layer of gravel with a large ship or other decoration.
Smaller decorations could become hidden, so you want to make sure the decorations are similar in size.
Determining How Much Gravel for Aquarium
There are 3 ways that you can figure out how much gravel you need for your aquarium.
a) The first way is to use the recommended method; 2 inches minimum in your tank, no matter the size or how many gallons of water.
b) The 2nd way is to use the suggested 1 to 1.5 pounds per gallon of water.
This means that a 5-gallon tank would need a minimum of 5 pounds of gravel.
c) Or, you can use a more in-depth way to figure out how much gravel you should use. In order to do it this way, you will need to locate a gravel calculator, online.
There are many of them and they all work about the same way. With the calculator, you enter the length and the width of your tank. You also enter the gravel depth that you want to achieve. You then have a drop-down menu to choose the type of gravel you want to use and then you hit the calculate button.
This tells you exactly how many pounds of gravel you need for your tank. 

Example: a tank that is 20 inches in length, 10 inches in width with pea-size gravel at 2 inches deep calculator out to 25.84 pounds of gravel. I found this calculator at aqua-calc.

We are not going to take a closer look at the different types of gravel that you can purchase for your aquarium. I will also cover the advantages and disadvantages of those types of gravel.

As stated before; gravel can add to the overall look of your tank but it is also going to aid in the growth of beneficial bacteria. If you are also choosing to have live plants in your tank, the gravel will aid in the growth of the live plants. This, in turn, helps to oxygenate the water for the fish. 

Why Gravel in Aquarium

Gravel is actually the most popular type of substrate for an aquarium. It is very affordable, comes in different sizes and colors and it is very versatile. The most popular style of gravel is smooth.

This ensures it doesn’t harm more delicate or vulnerable fish, but it still works well to anchor your plants. 

“If you choose a fish species with delicate fins, like a betta or a fantail goldfish, then you want gravel that does not have any sharp fragments that could tear their fins.”
“If you choose a bottom-dwelling species, such as a catfish, with sensitive whiskers you don’t want large or sharp gravel. It could tear off their whiskers as they scrounged for food down in the gravel.”

Gravel for Planted Tanks

Gravel will provide the roots of the plants with the perfect medium so they can root securely. If you have larger plants that have a more complex root system, you will need a deep layer of gravel.

This gives them plenty of room for their roots to spread out. To ensure your plants grow well and are healthy you will also need to have about a 1-inch thick layer of nutrients underneath your gravel.

Having the proper nutrients not only keeps your plants healthy but it will help in oxygenating the water, should you decide to add a fish or 2.

Types of Gravel for Aquarium

There are two main types: Colored and Pea Gravel

First and foremost, NEVER use gravel that is not specifically made for aquariums. Gravel from your driveway, for instance, can seriously harm your fish. You could be ultimately introducing parasites, bacteria, and other harmful elements into your tank by using gravel from the environment.

Colored Gravel

This gravel is very eye-catching in an aquarium, and kids love it. Colored gravel is found if you have fish that prefer higher pH levels or alkaline conditions, like an Oscar or Rift Lake Cichlid.

This type of gravel is made with natural Dolomite which contains high levels of calcium and magnesium. If you are 110% set on using the colored gravel then you will need to add a pH buffer to fix the water chemistry for your fish. 
If you have fish that require neutral or soft water, then you can purchase Inert Gravel. This type of gravel will not affect the water chemistry of the tank.

Pea Gravel

If you want your tank to have that natural look, then pea gravel is your go-to gravel. Pea gravel is fragments of assorted stones.

This is a type of inert grave because it has no substances that will alter the chemistry of your tank’s water. This type of gravel is performed under gravel filters and planted tanks. There are 2 disadvantages to pea gravel;

  • It contains a lot of dust and sand. This means it will take quite a bit of rinsing before you can put it in your tank. 
  • It also contains rough, sharp pieces which could harm certain fish.

Benefits Of Gravel In Aquarium

Gravel has many benefits; water flow, filters, clear water, beneficial bacteria, and it is better for your plants.

  1. Water Flow: Gravel is ideal if you have an under gravel filter because it allows the water to flow more freely than other types of substrate. Free-flowing water can help remedy air pockets. The air pockets will allow harmful bacteria to build up and could ultimately pollute the water.
  2. Filters: Unlike sand, gravel will stay on the bottom of the tank where it belongs. This causes no harm to the filtration system. Gravel also helps keep your water clear because it won’t stir-up, like sand, if you have fish that enjoy digging or burrowing in your substrate.
  3. Beneficial bacteria: No matter how big or small your gravel is, each piece is a place for the beneficial bacteria to grow. 5 pounds of gravel equals an abundance of “good” bacteria in your fish tank. Good bacteria helps your fish and your plants.
  4. Plants: As stated above, gravel is a heavier substrate, so it will anchor your plants more effectively. Fish waste will work itself down between the pieces of gravel, providing fertilizer for your plants. This in turn will help the plants grow and help keep the water oxygenated and the fish healthy.

Algae Growth

Gravel will also encourage algae growth, which fish keepers love and hate. You can look into adding algae-eating fish or 2 to help with the growth of the algae. There are some fish who enjoy the algae as part of their diet.

Gravel, for all of its benefits, also has drawbacks as well. It can be time-consuming to clean. Fish waste, uneaten food, and other types of debris fall through the gaps in the gravel. Depending on what it is, it will eventually begin to decompose. 

Some of the wasted food could be bloodworms, shrimp, or other live foods that some species of fish like to have on occasion. This will pollute the water and cause the quality of your water to fade. All of which could cause illness or death in your fish. Checking the water quality, with a test kit, on a regular basis is highly recommended. 

If you purchase gravel that is sharp or has pointy areas, it can harm fish with delicate fins or the fish who like to burrow in the substrate. It can also harm your decorative snails that some choose to have in their tanks. 

You will need to spend quite a bit of time rinsing the gravel before you can add it to your tank, or your water will instantly become cloudy. Even if the bag says, “Pre-washed” because it can still have fine dust all over it. So, if you have to rinse 20, 40, or 80 pounds of gravel, it could take a few hours.

How to Take Care of Aquarium Gravel

Pea gravel is the worst for containing dust and sandy particles that can plug your filters if it isn’t rinsed thoroughly.

Once your tank is established you need to make sure you “vacuum” your gravel on a regular basis to get rid of wanted food and general debris.

The vacuum or siphon cleaner you use will also remove water, so you can do your gravel cleaning during your weekly maintenance or water change.


The advantages, in my opinion, outweigh the disadvantages of using gravel for your aquarium. That is part of the reason that gravel is so popular, a lot of fish keepers have the same opinion. It’s popularity also comes from the fact that it is so versatile, affordable, and you have such a wide range of choices; from colored to natural-looking and more 

You want to make sure you remember to choose gravel that is beneficial for the fish you are going to house in your tank. If you are going to incorporate live plants, remember to add at least 1 inch of nutrients underneath the gravel.

You also want to remember to NEVER use environmental gravel! Only use gravel that is specifically packaged for aquariums. 

Last, but not least, the 3 ways that you can determine how much gravel you need to put into your aquarium;

  • 2 to 2.5 inches deep is the general rule, no matter how big the tank or how many gallons of water.
  • 1 pound of gravel per 1 gallon of water is what is suggested, and is the easiest method of calculation
  • Use a gravel calculator, which will determine how many pounds of gravel you need according to the length and width of your tank. 

The later of the 3 is going to be the most in depth or precise way to determine how much gravel you need. The first 2 methods are easier and quicker. But for the sake and the subject of this article- 1 pound of gravel per 1 gallon of water is how you determine how much gravel you need.

As with all aspects of fish keeping, make sure you research so you get all the prime items for the specific fish you want to have in your tank. The things you choose are going to determine whether you have healthy, happy fish.

Related Articles:

Eco-Complete vs Flourite Substrate, Which Is Best?
Using An Undergravel And A Power Filter Together: A Good Idea?
How Do You Treat a Bacterial Bloom?-Easy Guide


I'm passionate about fish pets and love sharing everything I learn about them.

Recent Posts