How Much Gravel for a Fish Tank?

Colorful fish with gray and multi-colored gravel for fish tank.

Having a fish tank in your home can be both fun and educational. Fish are beautiful and there are mental health benefits to having pets.

People who have fish or who are thinking about getting them may be unsure how much gravel to use in their fish tank. Let’s dive in to learn what amount of gravel is the right amount for your aquarium!

How Much Gravel for an Aquarium?

There are many types of gravel and decorations you could put in an aquarium, but as a rule, a tank should have one pound of gravel for each gallon of water it holds.

Why Fish Tanks Need Gravel

The gravel in fish tanks, which is also known as substrate, may be colorful, but it’s not there for decorative purposes. In fact, gravel plays an important role in keeping the fish in the tank healthy.

Gravel Makes a Friendly Fish Habitat

Gravel in a fish tank reduces reflections that may frighten fish. Some fish like to burrow and gravel allows them to do that, too.

High-quality fish tank gravel is also necessary to anchor plants and allow them to grow, and to provide a place for foraging fish to find food that their cohorts drop into the gravel. 

Gravel Provides Biological Filtration

In any fish tank, ammonia and nitrates can build up. The presence of sufficient gravel for the size of the tank provides water filtration to keep these harmful substances at bay and allow healthy bacteria to thrive.

Gravel Reduces Cleaning Time

Owning fish is a responsibility and part of that responsibility involves cleaning the fish tank regularly. Without gravel, cleaning must occur more frequently because there may not be enough healthy bacteria to keep the fish in good health.

Gravel Provides Support for Plants

Plants provide a pleasant habitat for fish and prevent the build-up of ammonia, nitrates, and carbon dioxide, which is essential in a heavily populated tank.

Are There Times When a Fish Tank Shouldn’t Have Gravel?

In most cases, fish tanks should have gravel because it creates an agreeable environment for the fish and provides health benefits. That being said, some species of fish, including rays and eels, prefer a sand substrate to a gravel one.

Additionaly, according to fish experts, there should be no gravel in a tank used to raise fish fry (very young fish) or to heal a sick fish. Fish fry are tiny and since gravel must be cleaned, there’s a risk of vacuuming up the fry along with any dirt or food scraps. Meanwhile, sick fish need water with exactly the right balance of nutrients and food scraps and bacteria in the substrate can make them sicker or even kill them.

Calculate How Much Gravel for a Fish Tank

It’s essential to put a sufficient amount of gravel in a fish tank to allow for proper filtration and create a healthy habitat for your fish. Calculating the amount of gravel needed isn’t difficult and can be done based on the size of the tank.

How Much Gravel for a Five Gallon Tank?

A five-gallon fish tank is small and doesn’t need much gravel to provide proper filtration and anchoring for plants. A tank this size needs no more than five pounds of gravel.

How Much Gravel for a 10-Gallon Tank?

In a 10-gallon tank, there’s more space and more water than in a five-gallon tank. To give fish the health benefits of a substrate or gravel cover, the tank should have about 10 pounds of gravel in it.

How Much Gravel for a 20-Gallon Tank?

Fish in a 20-gallon tank have a lot of space, provided the tank isn’t overcrowded with fish. With more water, there’s a need for more gravel. A tank with 20 gallons of water should have 20 pounds of gravel.

How Much Gravel for a 30-Gallon Tank?

A 30-gallon tank can hold a lot of fish, including larger species that need room to swim. A tank this size will need approximately 30 pounds of gravel substrate.

How Much Gravel for a 55-Gallon Tank?

Fish enthusiasts may opt for a 55-gallon tank to create a realistic habitat for a sizable population of fish. A large, 55-gallon tank will require a whopping 55 pounds of gravel to keep fish healthy and happy.

Tanks over 55 gallons may need as much as four inches of substrate.

Orange and yellow fish in fish tank with gravel and plants.

How to Gravel an Aquarium

After calculating how much gravel per gallon of water in a fish tank, it’s time to buy gravel and place it in the tank. 

What Type of Gravel to Buy

Some people may wonder if they can take rocks and gravel from outside and place them in a fish tank. Doing so may harm fish because natural rocks can alter the pH balance of the water or even release harmful bacteria that can affect the fish.

It’s a safer bet to buy gravel that is specifically made for fish tanks. Gravel comes in an array of sizes and colors. The size you choose should be based on the type of fish you have, since some species do better with large gravel while others prefer smaller gravel.

While gravel comes in bright colors, fish may prefer a more natural-appearing habitat. Glass gravel is not a good choice since it can be sharp and may break down more quickly than stone gravel. It doesn’t provide the same filtration benefits as natural gravel, either.

How to Save Money on Gravel

Gravel for fish tanks can be expensive, especially when a large tank is involved. Purchasing high-quality gravel is a must for healthy fish, but there are ways to save some money.

Keep in mind that painted gravel tends to be more expensive than natural gravel. It’s possible to add color to a tank in other ways, with decorations or plants, or even by scattering a small amount of glass gravel in with the regular substrate.

It may also be an option to buy gravel online at a lower price than in stores, or to get a bulk discount for a large purchase. 

Steps to Gravel a Fish Tank

There are several steps to follow before adding gravel to a fish tank.

  1. Make sure there is enough gravel to provide about two inches of cover at the bottom of the tank, or up to three to four inches for a tank with more than 55 gallons of water.
  2. Rinse your gravel or substrate first. This step is essential because it removes dust that could cloud the water and harm the fish.
  3. Place gravel in the tank before filling it. Adding gravel to a tank that already has water is tricky because some gravel may float and distribution at the bottom is unlikely to be even.

Plants should be added after the tank has been filled with water.

Tips for Cleaning Gravel in an Aquarium

Gravel does a good job of filtering water and keeping fish happy, but it does need to be cleaned. Gravel cleaning can be done with an aquarium vacuum. The vacuum will extract gravel particles that are too small as well as food fragments and waste.

With proper maintenance, there is no need to replace the gravel in a fish tank. Regular cleaning and water changes will help keep the gravel clean and allow it to filter water for a healthy habitat.

Gravel in a Fish Tank Keeps Fish Healthy

For healthy fish, most tanks need one pound of gravel for each gallon of water. Using natural gravel will provide fish with a suitable ecosystem where they can thrive. 

Different fish require different types of substrate, and some may prefer a sandy bottom. Use the information here to determine how much gravel is necessary for a fish tank and keep fish happy and healthy, whatever size tank they’re in.

This entry was posted in DIY, Home & Garden and tagged , . By Aimee Parrott