How much substrate to buy for the aquarium?

When planning a new aquarium, deciding how much substrate to buy is a big challenge, especially if you are a beginning hobbyist. How many bags of substrate are needed? Does sand fill less than gravel? Do you need more substrate for a planted tank? These are all questions I asked when I started my journey into the hobby of aquarium hobby.

How much substrate to buy for the aquarium?

Take a look at your local aquarium supply store and you will see that there are many brands and types of aquarium substrate. To further complicate matters, different manufacturers package their products in different volumes, making calculating how much you need even more complicated.

Aquarium substrate can also be expensive, so knowing how many bags you need to buy also helps you budget properly. I know the pain of coming home with five bags of expensive black aquarium sand, only to find out I only really needed four!

You can use an online aquarium storage calculator or substrate calculator to estimate how much sand or gravel you’ll need.

In this guide, we show you how to calculate exactly how much substrate you’ll need for your new tank, taking the guesswork out and potentially saving you a lot of money and hassle.

Substrate Calculator

The quickest and easiest way to calculate how much substrate you need is to use a substrate calculator.

A good substrate calculator will allow you to enter the dimensions of your tank, the type of substrate you want to use, whether or not the tank is going to be planted, and even the species of fish you want to keep.

How much substrate do you need?

The depth of substrate you need depends on several factors, including:

  • The size, volume and depth of your tank.
  • The species of fish you intend to conserve.
  • Whether you are using live or artificial plants.
  • What aquascaping design do you want to create?
  • your filtration system

As a general rule of thumb, if you’re using gravel, you need about 1.5 to 2 inches deep, closer to 2 inches if you have a filtration system under the gravel. If you want to use a mixed substrate, the depth requirement remains the same.

If you prefer to use sand, you’ll need a little less, and about 1 inch should do the trick. Note that if you have a filter under gravel, you cannot use sand, as the material is too fine and would clog the filter plates.

In all cases, if you plan to keep large burrowing fish or species that like to burrow in the substrate, you will need to add an inch or so.

planted tanks

Planted tanks look great and the presence of live plants can be beneficial to your fish, too, helping to lighten the bioload in your tank by utilizing nitrates in the water column.

Substrates are crucial for your plants to thrive and grow. Essentially, aquatic plants are very similar to garden plants in that they require nutrients, including magnesium, potassium, iron, and nitrogen, which they derive from the growing medium and water.

It is important to research the plant species you want to use as they have different requirements when it comes to substrate. For example, species like Anubias and Ferns don’t need a substrate at all, while Cryptocoryne needs a lot of room to accommodate its root system and prefers deeper cover at the bottom of the tank.

You can use a sloped substrate to create a more three-dimensional aquascape that suits larger plants with longer root systems. However, 2 to 3 inches of gravel or sand is generally sufficient for most plant species.

nutrient layer

The coloration, growth rate, and general health of plants depend on the availability of nutrients in the aquarium, so when creating a planted aquarium, you must include a nutrient layer below the substrate layer.

Spread the nutrient layer on the bottom of your tank to a depth of about an inch. Cover that with two inches of gravel. If you have an aquarium larger than 55 gallons, you will need to increase the layer of gravel or sand up to 3 inches deep.


The amount of substrate you use in your aquarium depends on a few factors, including the size of your tank, the species of fish you want to keep, and whether you intend to have live plants. Ideally, you should have about 1.5 to 2 inches of gravel or sand, a little more than that if you have rooted plants as well. Additionally, plants require an additional inch of nutrient medium below the substrate.

You can use our substrate calculator to calculate exactly how much substrate you need, or grab a pen and paper and use the simple manual calculation we’ve included above.

If you have any questions about how much substrate to use or what type of substrate would be the best choice for your aquarium, please put them in the comments box below.

We will do our best to provide you with the information you need.

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