A Complete Guide to Aquarium Substrates

The substrate forms the foundation of every aquarium. More than just a decorative layer, it plays a vital role in supporting beneficial bacteria, anchoring aquatic plants, influencing water chemistry, and creating a natural environment for your fish. Choosing the right substrate can make maintaining your aquarium easier while improving the health of your livestock and enhancing the overall appearance of your aquascape.

With so many options available—from natural gravel and sand to nutrient-rich aquasoils and specialised substrates—it can be difficult to know which is best for your aquarium. The right choice depends on the type of aquarium you want to create, the fish you plan to keep, and whether you’ll be growing live plants.

In this guide, we’ll explain the different types of aquarium substrates, their advantages and disadvantages, and how to choose the best option for your freshwater aquarium.

What Is Aquarium Substrate?

Aquarium substrate is the material placed on the bottom of an aquarium.

It serves several important purposes:

Provides a natural appearance
Supports beneficial bacteria
Anchors live plants
Allows fish to display natural behaviours
Collects nutrients for plant roots
Influences water chemistry (depending on the type)

Choosing the correct substrate is one of the first decisions you’ll make when setting up an aquarium.

Why Is Substrate Important?

While some fish can live in bare-bottom aquariums, most freshwater aquariums benefit greatly from having a substrate.

Benefits include:

Increased biological filtration
Improved aesthetics
Better plant growth
Reduced stress for fish
Natural digging behaviour
Enhanced aquascaping opportunities

Types of Aquarium Substrate

There are several main categories available.

Gravel

Gravel is one of the most popular aquarium substrates.

Advantages:

Easy to clean
Wide variety of colours
Doesn’t compact easily
Suitable for beginners
Excellent water circulation

Available in:

Natural gravel
Coloured gravel
Fine gravel
Large decorative gravel

Most community aquariums perform well with gravel.

Sand

Sand creates a beautiful natural appearance.

It’s particularly suitable for:

Corydoras
Loaches
Freshwater rays
Shrimp
Soft-water biotopes

Advantages include:

Natural appearance
Gentle on bottom-dwelling fish
Excellent for burrowing species
Prevents food becoming trapped between stones

Fine aquarium sands are available in:

Natural beige
White
Black
Dark brown

Aquasoil

Aquasoil has become the preferred substrate for planted aquariums and aquascaping.

Benefits include:

Nutrient rich
Promotes strong root development
Encourages rapid plant growth
Buffers pH in many cases
Ideal for carpeting plants

Popular aquasoils are specifically designed for aquatic plants and should not be confused with ordinary garden soil.

Laterite and Plant Substrates

These are nutrient-rich layers designed to sit beneath gravel or sand.

They provide:

Iron
Trace elements
Root nutrients

Often used beneath decorative substrates in planted aquariums.

Bare Bottom

Some aquariums use no substrate at all.

Common in:

Quarantine tanks
Breeding aquariums
Hospital tanks
Fish rooms

Advantages include:

Easy cleaning
Better waste removal
Simple observation

However, they lack the natural appearance most hobbyists prefer.

Choosing the Right Substrate

Consider several factors.

Aquarium Type

Community Aquarium

Good choices include:

Natural gravel
Fine gravel
Sand

Planted Aquarium

Best options:

Aquasoil
Nutrient-rich substrates
Fine gravel with root tabs

Goldfish Aquarium

Choose:

Smooth gravel
Fine sand

Avoid sharp substrates that may damage sensitive mouths.

Shrimp Aquarium

Fine substrates work particularly well.

Many shrimp keepers choose dark substrates to enhance shrimp colouration.

Cichlid Aquarium

Depends on species.

African cichlids often appreciate sand for digging.

South American cichlids benefit from fine natural substrates.

Choosing the Right Grain Size

Grain size affects both appearance and maintenance.

Fine Sand

Best for:

Corydoras
Loaches
Shrimp
Burrowing fish

Medium Gravel

Ideal for:

Community aquariums
Beginners
General freshwater setups

Larger Gravel

Suitable for:

Decorative displays
Large fish

May trap more debris between stones.

Aquarium Plants and Substrate

Healthy plants depend heavily on substrate selection.

Root-feeding plants include:

Amazon Swords
Cryptocoryne
Vallisneria
Dwarf Sagittaria

These perform best in nutrient-rich substrates or with root tabs.

Plants such as:

Java Fern
Anubias
Bucephalandra

attach to wood or rocks rather than growing in substrate.

How Much Substrate Do You Need?

Most aquariums benefit from:

Front: 3–5 cm

Rear: 6–10 cm

Creating a gentle slope:

Improves appearance
Adds depth
Helps with aquascaping

Heavily planted aquariums often require deeper substrates.

Should You Rinse New Substrate?

Gravel

Yes. Rinse thoroughly until the water runs clear to remove dust and manufacturing residue.

Sand

Also requires thorough rinsing. Some cloudiness during the first fill is normal.

Aquasoil

Most manufacturers recommend not rinsing aquasoil. Always follow the instructions supplied with the product.

Substrate Depth

Too little substrate:

Restricts root growth
Looks unnatural

Too much substrate:

May compact
Creates anaerobic pockets
Makes maintenance harder

Aim for a balanced depth based on your aquarium type.

Can You Mix Different Substrates?

Absolutely.

Many aquascapers combine:

Sand foregrounds
Gravel pathways
Aquasoil planting areas
Decorative rocks

Using substrate separators helps prevent mixing over time.

Aquarium Root Tabs

Root tabs are fertiliser capsules placed beneath plant roots.

Useful when using:

Gravel
Sand
Inert substrates

They supply:

Iron
Potassium
Trace elements

without affecting the entire aquarium.

Does Substrate Affect Water Chemistry?

Some substrates are chemically active.

Aquasoils

Often lower:

Suitable for:

Shrimp
Soft-water fish
Aquascaping

Crushed Coral

Raises:

Often used in African cichlid aquariums and marine systems.

Always choose a substrate compatible with your livestock.

Cleaning Aquarium Substrate

Regular cleaning prevents waste build-up.

Gravel

Use a gravel vacuum, lifting and lowering the siphon to remove debris.

Sand

Hover the siphon just above the surface to remove waste without removing excessive sand.

Avoid deep stirring unless necessary.

Beneficial Bacteria

Substrate provides a large surface area for beneficial bacteria.

These bacteria convert:

Ammonia
Nitrite

into nitrate, helping maintain biological stability.

Fish That Love Sand

Many species naturally sift through sand.

Examples include:

Corydoras
Kuhli Loaches
Geophagus
Freshwater Gobies
Freshwater Stingrays

Using gravel with these fish may damage their sensitive barbels or mouths.

Fish That Dig

Many fish enjoy rearranging substrate.

Examples include:

Convict Cichlids
Oscars
Geophagus
Goldfish

Choose smooth substrates that won’t cause injury.

Algae and Substrate

Substrate itself doesn’t cause algae.

However:

Excess waste
Overfeeding
Poor maintenance

allow nutrients to accumulate.

Regular vacuuming helps prevent algae problems.

Decorative Coloured Gravel

Brightly coloured gravel remains popular for children’s aquariums.

While generally safe if designed for aquarium use, many hobbyists prefer natural colours because they:

Look more realistic
Reduce fish stress
Complement live plants

Popular Aquarium Substrate Brands

Some of the leading manufacturers include:

Tropica
Fluval
JBL
Dennerle
Colombo
Aquael
Oase
Seachem
TMC
SuperFish

Each offers substrates designed for different aquarium styles and livestock.

Common Mistakes

Choosing Appearance Over Function

A substrate should suit both your fish and your plants—not just your décor.

Using Sharp Gravel

Sharp stones may injure bottom-dwelling species such as Corydoras and loaches.

Making the Substrate Too Deep

Very deep substrate can become compacted, reducing water circulation and encouraging anaerobic zones.

Skipping Gravel Vacuuming

Waste naturally settles into substrate.

Routine cleaning helps maintain healthy water quality.

Not Considering Plant Requirements

Heavy root feeders require nutrient-rich substrates or regular root fertilisation.

Which Substrate Is Best?

Aquarium Type	Recommended Substrate
Community Aquarium	Natural Gravel
Planted Aquarium	Aquasoil
Shrimp Tank	Aquasoil or Fine Gravel
Corydoras Aquarium	Fine Sand
Goldfish Aquarium	Smooth Gravel or Sand
Aquascape	Aquasoil
Cichlid Aquarium	Sand or Crushed Coral (species dependent)

Final Thoughts

The right substrate forms the foundation of a healthy, attractive aquarium. Whether you’re creating a colourful community aquarium, a lush planted aquascape, or a specialist biotope, choosing a substrate suited to your fish, plants, and maintenance routine will make a significant difference to your aquarium’s long-term success.

Natural gravel remains an excellent all-round choice for many freshwater aquariums, while nutrient-rich aquasoils provide outstanding results for planted tanks. Fine sand is ideal for bottom-dwelling fish and biotope aquariums, offering a natural environment that encourages instinctive behaviours.

At Charterhouse Aquatics, we stock a wide range of aquarium substrates, including gravel, decorative sand, nutrient-rich aquasoils, plant substrates, root tabs, and aquascaping materials from leading brands such as Tropica, JBL, Fluval, Dennerle, Seachem, Oase, Aquael, and Colombo. Whether you’re setting up your very first aquarium or creating an award-winning aquascape, our expert team can help you choose the perfect substrate for your freshwater aquarium.