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Home > Fish > How to Make a Deep Sand Bed for Aquariums in 6 Easy Steps

How to Make a Deep Sand Bed for Aquariums in 6 Easy Steps

fish swimming inside aquarium with sand bed

Many freshwater aquarium keepers aren’t familiar with deep sand beds and the numerous benefits associated with them. Deep sand beds are a form of natural water filtration that allows for the cultivation of beneficial bacteria in the lower levels of sand. These bacteria help to reduce nitrates naturally. Deep sand beds also help improve water quality, support plant growth, enhance the environment for your fish, and decrease the need for electronic filtration.

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Necessary Supplies
  • Coarse, large grain sand
  • Plants that root in substrate
  • Submersible pump or power filter
Optional Supplies
  • Burrowing/digging fish
  • Malaysian trumpet snails
  • Other freshwater snails
  • Freshwater scuds
  • Freshwater clams
  • Blackworms
  • Freshwater shrimps
  • Soil

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The 6 Easy Steps to Set Up Your Deep Sand Bed

1. Place 3–6 inches of coarse sand in the tank.

You will need a coarse sand for your deep sand bed. The smaller and more densely packed the sand is, the less movement and oxygenation will be available for bacterial growth. You should select sand that has a uniform size throughout. The recommendation is for the sand to be approximately 0.5 mm in size but sand up to 2 mm can be used.

The larger the sand grain is, the deeper you will need the sand bed to be. For 0.5 mm sand, 3–4 inches should suffice. For sand up to 2 mm, you may need 5–6 inches or more. Some deep sand beds may need to be as much as 8 inches deep for maximum efficacy.

You can add a layer of soil below the top 1 inch of sand, or you can simply mix the sand and soil together below the sand cap. This will create a more nutritious substrate for plant life.

person adding substrate and sand in the tank
Image Credit: Krysja, Shutterstock

2. Fill and cycle the tank.

Once the sand is in place, go ahead with filling the tank. Make sure to treat the water for chlorine if using tap water. Ideally, you should go ahead and begin cycling the tank before you add any animals. It’s possible to perform a fish-in-tank cycle, but it isn’t ideal and does risk injury, illness, and death for your animals.

To cycle the tank more quickly, you can add substrate from a well-established tank to help inoculate your new substrate with the beneficial bacteria from the established tank’s substrate.


3. Install a filter.

Since a deep sand bed will function as filtration for your tank, you only need filtration enough to oxygenate the water and provide adequate water movement for your tank livestock. Generally, it’s recommended to use a filter rated for half the size of your tank. This is because overfiltration can decrease the growth of beneficial bacteria in a deep sand bed.

Aim for a filter that will remove solid particles from the water, also known as mechanical filtration. This will help keep the water cleaner than just having a deep sand bed since the beneficial bacteria in the substrate will not be able to remove free-floating waste particles, food, and plant matter in the water.

aquarium filter
Image Credit: Andrey_Nikitin, Shutterstock

4. Add the plants.

Once the water has been added and dechlorinated, you’re ready to add the plants. Plants with extensive root systems are ideal for this type of setup since they will help to anchor the substrate and pull some waste products from the substrate as well. Plants are an essential part of keeping a deep sand bed. Without plants, hydrogen sulfide gas may build up in the substrate, which can cause an unpleasant smell when released.

What plants you choose will depend on the needs of your tank. Not all plants are suitable for all water parameters required by your fish and invertebrates. Some good options include Amazon Swords, Vallisneria, Ludwigia, and Crypts, which are root-feeding plants that can put out extensive root systems.


5. Introduce invertebrates.

Once the tank is fully cycled and your plants are settled in, it’s time to add your invertebrates. A variety of invertebrates are best because each can serve a different purpose in the tank. Malaysian Trumpet snails are burrowing snails that can help to keep your substrate turned over, oxygenated, and free of hydrogen sulfide. Blackworms are also a good option to add burrowers to your tank.

Freshwater clams are filter feeders that dig in substrate, so they will help turn the substrate and keep the water clear. Shrimp and non-burrowing snails, like Nerites, will work to clean waste from the upper portion of the substrate, as well as helping keep the tank walls and plants clear of algae. Freshwater scuds are arthropods that will help reduce waste in your tank and help feed your plants.

Many small invertebrates, especially shrimps, scuds, and blackworms, are very prone to being eaten by fish. You may have to replenish their numbers over time if your fish find them to be a good snack. The more densely planted your tank is, the more places your invertebrates will be able to hide, keeping their numbers stable.

Yellow apple snail with shell covered with green algae
Image Credit: Corneliu LEU, Shutterstock

6. Introduce the fish.

Now that everything and everyone else are settled into the tank, it’s time to add fish. You can add any fish you’d like, but fish that enjoy burrowing or digging in substrate are an ideal addition to a tank with a deep sand bed. Goldfish, Kuhli loaches, Horseface loaches, and Geophagus species are all excellent fish if you’re in search of fish that will dig or burrow in substrate.

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An Alternative

If setting up and maintaining a deep sand bed in your tank doesn’t sound worth it to you, you can also look into the addition of a refugium. A refugium is often set up as part of saltwater tanks in order to protect especially delicate plants and animals, but they can be set up for freshwater tanks as well. A refugium would allow you to maintain populations of invertebrates without risking them being eaten by your fish.

The downside to adding a refugium instead of an in-tank deep sand bed is that a refugium will need to be large enough to maintain proper filtration for your main tank. A 100-gallon aquarium with a 10-gallon refugium isn’t going to get the full benefits of a deep sand bed. It’s ideal for a deep sand bed to be built into the tank itself for maximum space.

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In Conclusion

A deep sand bed may not be the top option for every tank, but it can be a beneficial way to maintain your tank’s water quality naturally. It’s easiest to set up a deep sand bed for a new tank, but you can add one to an already established tank if desired. You may need to move out fish, invertebrates, and plants to do so, though, so be prepared to have an alternate location for everything to stay while you transition the primary tank over to a deep sand bed.

Also See: Adding Chemicals or Additives to Goldfish Tank: Is it Necessary?


Featured Image Credit: Michael_Luenen, Pixabay

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