When setting up an aquarium choosing the right substrate is one of the most important decisions you'll make. Whether you're creating a planted tank or simply need a good foundation for your fish, the substrate plays a critical role in plant growth, water chemistry, and overall tank health. In this guide, we’ll cover everything you need to know about aquarium substrates—from the different types available to how each one can affect your plants and fish, and how to set up your tank properly with substrate.

 

1. What Is Aquarium Substrate?

Substrate is the material that covers the bottom of your aquarium. It’s not just for looks, it serves several essential functions such as:

 

Supporting Plant Growth:

Substrate can provides a solid base for plant roots to anchor and grow.

 

Helps with Filtration:

Beneficial bacteria can colonise the substrate which aids in biological filtration and can help break down fish waste.

 

Affects Water Chemistry:

Substrates can influence pH, hardness, and nutrient availability within the water column and the substrate itself.

 

Enhances Aesthetics:

The right substrate can bring your aquascape to life, whether that's creating a natural environment, a beach type environment or a ornamental style with colourful gravel and ornaments!

 

2. Why Substrate Is Important for Your Aquarium

The right substrate is vital for promoting healthy plants, maintaining stable water chemistry, and creating the best environment for your fish to thrive.

 

Here are the benefits of using the proper substrate in your tank:

 

Healthy Plant Growth:

Most plants require nutrients from substrates for strong root development, especially for heavy root feeders such as the Amazon Sword plant, for plants such as this and other high tech plants, nutrient rich substrate is crucial.

 

Improved Filtration:

Substrates provide surface area for beneficial bacteria to help break down waste and maintaining a healthy tank ecosystem.

 

Stabilized Water Chemistry:

Some substrates can buffer pH levels and help maintain stable water parameters, which is essential for both plants and fish.

 

3. Types of Aquarium Substrates

Each type of substrate has its unique properties, and choosing the right one depends on the needs of your tank whether it’s a fish only setup or a planted aquascape.

 

1. Gravel

Gravel is a commonly used substrate made of small, rounded stones or pebbles. It’s one of the more affordable, easy to find, and readily available in various colours and sizes.

 

 

Impact on Water Chemistry:

Gravel is generally pH neutral which makes it a safe choice for most fish species.

 

Best for:

Fish only or low tech planted tanks with slow growing plants is recommended for gravel substrates.

 

• Pro Tip: If using gravel in a planted tank, you will need to add supplements such as root tabs and/or liquid fertilisers, as gravel doesn’t provide the essential nutrients for plant growth!

 

Pros: Very easy to clean and has good water circulation which can be good for beneficial bacteria to grow on helping your aquarium filter out all the bad stuff.

 

Cons: Does not provide nutrients for plants and root growth can be quite limited.

 

2. Sand

Sand is another popular choice for aquarium substrates. Its fine texture creates a smooth, clean look and is ideal for bottom dwelling fish, can come in many different natural colours.

 

 

Impact on Water Chemistry:

Sand is generally pH-neutral and inert (doesnt provide minerals for plants) and can compact easily which reduces water flow within the substrate potentially creating anaerobic pockets (ammonia pockets) if not cared for correctly.

 

Best for:

Tanks with bottom dwelling fish such as Corydoras, catfish, loaches, African cichlids and other fish species that may like to sift through the sand.

 

• Tip: Avoid using this substrate for plants as sand has no nutrients and is too dense, because sand is so dense it doesn't allow plants to grow form a strong root system.

 

• Pro Tip: If you do plan on using a sand substrate for catfish or Corydoras opt in for a finer sand as it is more suitable for their living conditions, I would recommend play sand or pool filter sand as it is very fine and is much more inexpensive compared to "aquarium sand". If you do opt in for a more course sand it may damage catfish's barbells causing them pain and discomfort.

 

Pros: Aesthetic smooth texture, has a natural beach look and is excelent for certain fish species.

 

Cons: No nutrients for plants and can cause anaerobic zones or "ammonia pockets" if the substrate is too deep, sometimes if accidently disturbed the pocket can open up and release ammonia into the water column.

 

3. Aquasoil

Aquasoil is a nutrient rich substrate designed specifically for planted tanks. It often contains a mixture of clay, minerals, and other organic matter that can support healthy plant growth.

 

 

Impact on Water Chemistry:

Aquasoil can lower the pH and soften water which can be beneficial for certain plant species and fish that prefer slightly acidic water.

 

Best for:

High tech planted aquariums with fast growing and heavy root feeding plants such as Amazon swords.

 

• Pro Tip: Aquasoil may cloud the water and leak ammonia into the water column when first added, so be sure to let the tank sit for a few days with a filter running, monitor the water chemistry and do water changes as necessary until water conditions are safe before adding in any fish.

 

Pros: Excellent for plant growth and is nutrient rich.

 

Cons: Can deplete nutrients over time and may require top ups or replacements.

 

4. Laterite

Laterite is a clay-based substrate rich in iron and minerals that are beneficial to heavy root feeding plants. It is often used as a supplement in combination with other substrates.

 

 

Impact on Water Chemistry:

Laterite is neutral in terms of pH but is rich in iron which can support plant health.

 

Best for: 

Tanks with nutrient hungry plants, red plants and heavy root feeders.

 

• Pro Tip: Layer Laterite underneath a regular substrate (such as gravel) to avoid it from floating or clouding the water column.

 

Pros: High iron content and is excellent for heavy root feeding plants.

 

Cons: Messy when disturbed and may need to be capped with a different substrate.

 

5. Buffering Substrates (Crushed Coral, Lava Rock, etc.)

Buffer substrates, like crushed coral, lava rock, or ceramic rings do not provide any nutrients for plants but can significantly influence water hardness and PH.

 

 

Impact on Water Chemistry:

Inert substrates tend to raise pH and water hardness making them ideal for species that prefer alkaline water, such as African cichlids.

 

Best for: Fish that require harder and more alkaline water conditions.

 

• Pro Tip: Buffer substrates can be used in fish only tanks and may not be suitable for planted tanks without added fertilisers.

 

Pros: very long lasting, increases water circulation and helps maintain stable PH.

 

Cons: No nutrients for plants and may require supplements such as root tabs and liquid fertilisers.

 

6. Organic Soil

Organic soil substrates are made from decomposed plant material or terrestrial soil. It’s rich in nutrients and ideal for growing plants.

 

 

Impact on Water Chemistry:

Organic soil tends to lower pH and soften water. It can also release nutrients into the water column over time which is great for plants that can't be planted such as Anubias which feed on nutrients within the water column.

 

Best for:

Planted tanks, especially those aiming for a natural aesthetic.

 

• Tip: Organic soil can be messy and may cloud the water at first. Consider capping it with a layer of gravel or sand to prevent floating debris.

 

• Pro Tip: If you plan on using organic Soil make sure it is free of any contaminates and make sure you purchase it from a reliable resource. If the soil is contaminated by anything such as weed killers or pesticides it will completely destroy your aquariums ecosystem!

 

Pros: High in nutrients and is great for plant growth.

 

Cons: Can cloud water initially and may need to be topped up over time.

 

4. How to Set Up Your Tank with Substrate

Setting up your tank with the right substrate is essential to ensure plant and fish health as well as water balance. 

 

Here’s how to do it:

 

Step 1: Choose Your Substrate

Select the right substrate based on your tank’s needs:

 

Low-tech tanks:

Gravel or sand will be the option for you if you don't want any plants you can also opt in for creating rock display instead!

 

Planted tanks:

Aquasoil will support healthy root systems and robust plant growth.

 

Fish-only tanks:

Inert substrates like crushed coral can help create the right water chemistry depending on what fish species you are wanting to keep.

 

Step 2: Prepare the Tank

Ensure your tank is clean and free of dust and debris (do not clean with soap or bleach!). If you decide on using a nutrient-rich substrate, consider laying down a layer of laterite at the bottom for added support.

 

Step 3: Add the Substrate

Pour your chosen substrate evenly across the bottom of the tank. Aim for a depth of 5-7 cm for most substrates, and for sand, keep the layer thin (2-5cm) to prevent compaction and ammonia pockets.

 

Step 4: Fill the Tank with Water

Slowly add water to your tank. To do this you can use a plate or bowl, place the plate/bowl on top of the substrate and gently dispersing water onto it instead of directly adding water to the tank, this prevents you from disturbing the substrate and leaking excess ammonia and debris into the water column.

 

Once filled allow the water to settle before moving on to the next steps:

 

Step 5: Test Water Parameters

Once your tank is set up, test the water to ensure the pH, water hardness, and other parameters are within the desired or necessary range for the fish you would like to keep and adjust if necessary using water conditioners or buffers.

 

• Tip: some aquasoil and organic soil material may leak ammonia into the water column, to overcome this you may need to let the water sit for a few days with a running filter, test the water with a test kit every day and do a partial 20% water change afterwards until all levels are safe enough for you to introduce fish!

 

5. Maintaining Your Substrate

Proper substrate maintenance is key to a healthy aquarium, this can be achieved by:

 

Cleaning Regularly:

Use a gravel vacuum to remove debris from the substrate surface. This helps keep the tank clean and prevents waste build-up.

 

• Tip: If heavily planted most nutrient rich substrates do not need to be gravel vacuumed as the plants will feed on any debris in the substrate.

 

Monitoring Water Chemistry: 

Regularly test your water to ensure your substrate isn’t altering PH or hardness beyond the desired range.

 

Adding Fertilisers:

If using a substrate that doesn’t provide nutrients (like gravel) use root tabs or liquid fertilisers to support plant health.

 

6. Conclusion

Your choice of substrate can significantly impact the success of your aquarium. Whether you opt for nutrient rich aquasoil, classic gravel, or an inert substrate, each option has its strengths and considerations.

By carefully selecting and setting up the right substrate, you’ll create an environment that supports both healthy plants and fish!

 

• Pro Tip: If you’re new to setting up a planted tank, start with a nutrient rich substrate like aquasoil, as it will give your plants the best chance for success. As you gain experience, you can experiment with different substrate combinations to see what works best for you and your setup!

 

By following this guide, you will find the right fitting for you and your aquarium, and will be set up and running in no time!

 

 

 

My Tank is Already Established! How Do I Add More Substrate or Change It Out?

If your aquarium is already set up and you’re thinking about adding more substrate or replacing it, don’t worry, it’s totally doable with a little planning!

Whether you’re looking to add a layer of new substrate to give your plants a nutrient boost or completely change out your substrate to refresh your tank, our guide on How to Add or Change Substrate in an Established Aquarium covers everything you need to know! From how to avoid disturbing your tank’s ecosystem to maintaining water quality during the transition, we’ll walk you through each step to ensure a smooth process for your plants, fish, and overall tank health!