How Many Bags of Substrate is Needed?

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When planning a new aquarium, deciding how much substrate to buy is a major challenge, especially if you’re a beginner hobbyist. How many bags of substrate is needed? Does sand go further than gravel? Do you need more substrate for a planted tank? All these are questions that I asked when I began my journey into the fishkeeping hobby.

Take a look around your local aquarium supplies store, and you’ll see that there are many brands and types of substrate to choose from. To further complicate matters, the various manufacturers package their products in different volumes, and that makes working out how much you need even trickier. Aquarium substrate can be expensive too, so knowing how many bags you need to buy also helps you to budget correctly. I know the pain of getting home with five bags of expensive black aquarium sand, only to discover that I only actually needed four!

You can use an online aquarium stocking calculator or substrate calculator to work out how much sand or gravel you will need.

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

Substrate Calculator

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

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

How Much Substrate Do You Need?

Aquarium decoration in beautiful background

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

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

As a general rule of thumb, if you’re using gravel, you need around 1.5 to 2 inches depth, closer to 2 inches if you have an under gravel filtration system. 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 around 1 inch should be sufficient. Note that if you have an under gravel filter, you can’t use sand, as the material is too fine and would clog the filter plates.

In all cases, if you plan on keeping large fish that dig or species that like to burrow into the substrate, you’ll need to add another inch or so.

Planted Tanks

A green beautiful planted tropical freshwater aquarium with fishes

Planted tanks look great, and the presence of living 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 if your plants are to thrive and grow. Essentially, aquatic plants are much the same as garden plants in that they need nutrients, including magnesium, potassium, iron, and nitrogen, which they derive from the substrate and the water.

It’s important to research the species of plants that you want to use, as they have different requirements when it comes to the substrate. For example, species such as Anubias and Ferns don’t need a substrate at all, whereas Cryptocoryne needs plenty of space to accommodate its root system and prefers a deeper covering on the bottom of the tank.

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

Nutrient Layer

Aquarium with plants and reefs.

The coloration, growth rate, and overall health of the plants are dependent on the availability of nutrients in the aquarium, so when creating a planted aquarium, you should include a nutrient layer underneath the layer of the substrate.

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


hands of aquarist planting water plant echinodorus in new aquarium

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

You can use our substrate calculator to work out 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 concerning how much substrate you should use or what kind of substrate would be the best choice for your aquarium, please enter them in the comments box below.

We’ll do our best to give you the information that you require.

Alison Page has been an avid fish keeper for over 35 years and has owned many different species of freshwater tropical fish including bettas. Currently Alison has two large freshwater tanks. The first tank has two huge fancy goldfish who are almost ten years old and still looking as good as ever. In the other, she has a happy community of tiger barbs, green tiger barbs, corydoras catfish, platys, and mollies.

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