Seachem Flourite Black Sand 7kg – Planted Aquarium Substrate

Create a striking, long-lasting foundation for your planted aquarium with Seachem Flourite Black Sand 7kg, a naturally dark porous clay substrate designed specifically for freshwater planted aquariums.

The larger 7kg bag is ideal for creating complete substrate beds, covering larger aquarium areas or building deeper planted sections within an aquascape.

Its dark black appearance provides excellent contrast against green and red aquatic plants, colourful fish, freshwater shrimp, rocks and driftwood, helping create a dramatic planted aquarium display.

Unlike active aquasoils, Flourite Black Sand is a stable planted aquarium substrate designed to have minimal impact on aquarium pH. It can be used as the complete substrate bed and is designed to remain in the aquarium long term without requiring routine replacement.

Key features and benefits

• Designed for planted aquariums – Made specifically for freshwater planted tanks and aquascaping.
• 7kg larger pack – Ideal for complete substrate beds and larger planted aquarium areas.
• Dark black appearance – Creates striking contrast against aquatic plants, fish, shrimp, rocks and driftwood.
• Porous clay substrate – Provides a suitable substrate environment for aquatic plant roots.
• Stable and long-lasting – Designed to remain part of the aquarium without routine substrate replacement.
• Minimal effect on pH – A useful alternative when you don't want an active aquasoil deliberately altering water chemistry.
• Fine sand-like texture – Creates a detailed, natural-looking aquarium floor.
• Can be used on its own – Suitable as the complete substrate bed without requiring another substrate.
• Not chemically coated or treated – A naturally dark porous clay substrate rather than coated decorative gravel.

Product specifications

Brand: Seachem
Product: Flourite Black Sand
Colour: Black
Pack Size: 7kg
Substrate Type: Porous clay planted aquarium substrate
Suitable for: Freshwater planted aquariums and aquascaping
Water Chemistry: Stable substrate with minimal effect on aquarium pH
Use: Can be used as the complete aquarium substrate bed

Why choose Flourite Black Sand?

Flourite Black Sand combines a substrate designed specifically for planted aquariums with the visual impact of a dark aquarium floor.

The black substrate provides strong contrast against aquatic plants, helping green foliage appear brighter and making red plants particularly striking.

Colourful fish and freshwater shrimp can also stand out beautifully against the darker background.

This makes Flourite Black Sand an excellent option when both plant performance and aquascape appearance are important.

Why choose the 7kg bag?

The larger 7kg bag is a practical choice when you're creating a substantial substrate bed rather than covering a small feature area.

It's particularly useful for:

• Larger planted aquarium footprints
• Complete Flourite Black Sand substrate beds
• Deeper planted areas
• Aquascapes with slopes and raised sections
• Larger rooted aquarium plants
• Creating greater substrate depth toward the rear of the tank
• Combining multiple bags for larger aquariums

For smaller aquariums or feature areas, the 3.5kg Flourite Black Sand may be more suitable.

Is Flourite Black Sand an aquasoil?

No. Flourite Black Sand is better described as a stable porous clay planted substrate.

Active aquasoils are often selected because they influence aquarium water chemistry and can create softer, more acidic conditions.

Flourite Black Sand is designed to have minimal impact on aquarium pH.

This makes it a good option when you want a specialised planted aquarium substrate while maintaining greater control over your aquarium's water parameters.

Flourite Black Sand vs active aquasoil

Both products can provide excellent foundations for planted freshwater aquariums, but they work differently.

Active aquasoil may be appropriate when you specifically want your substrate to influence water chemistry.

Flourite Black Sand is better suited when you want a stable, long-lasting substrate without deliberately buffering the aquarium toward softer or more acidic conditions.

Flourite is also designed to remain in the aquarium long term rather than relying on temporary buffering properties.

Flourite Black Sand vs regular Flourite Sand

Both products are porous clay substrates designed for planted freshwater aquariums.

The main difference is appearance.

Flourite Black Sand creates a dark aquarium floor and provides strong contrast against plants and livestock.

Flourite Sand provides a lighter, more natural earthy appearance.

Choose between them primarily according to the style of aquarium or aquascape you're creating.

Is Flourite Black Sand good for aquarium plants?

Yes. Seachem Flourite Black Sand is specifically designed for planted freshwater aquariums.

Its porous clay structure provides a stable substrate environment where aquatic plant roots can establish.

Healthy aquarium plant growth also depends on appropriate lighting, carbon dioxide availability, nutrients and the requirements of the individual plant species.

Does Flourite Black Sand contain fertiliser?

Flourite Black Sand is best considered a plant-friendly mineral substrate rather than a complete fertiliser.

Its porous clay composition provides a suitable environment for aquatic plant roots but does not eliminate the need for appropriate plant nutrition.

Depending on your plants and aquarium setup, root tabs, water-column fertilisers or another suitable fertilisation method may still be required.

Does Flourite Black Sand affect aquarium pH?

Seachem Flourite is designed to have minimal impact on aquarium pH.

This is one of its important differences from active aquasoils.

If particular water parameters are important for your fish, shrimp or plants, regularly test your aquarium water and manage those parameters according to the requirements of your livestock.

Does Flourite Black Sand need replacing?

Flourite is designed as a long-lasting aquarium substrate.

It does not require routine replacement simply because it has been in the aquarium for an extended period.

This makes it particularly useful in established planted aquariums, where replacing the entire substrate bed could significantly disturb established plants and aquascaping.

How to use Seachem Flourite Black Sand

Prepare the substrate according to the instructions supplied with the product.

Add the prepared Flourite Black Sand to the aquarium and shape the substrate according to your aquascape.

A shallower layer toward the front with greater depth toward the rear can provide additional rooting space while creating visual perspective.

Deeper sections can also be created for larger rooted plants or elevated aquascaping areas.

Plant your aquatic plants carefully into the substrate before filling the aquarium.

Add water slowly to minimise disturbance and initial cloudiness.

Does Flourite Black Sand need rinsing?

Yes. Flourite products can contain fine dust generated during transport and handling, so pre-rinsing is recommended before use.

Rinse carefully to remove loose dust before placing the substrate into the aquarium.

Some initial cloudiness may still occur. Filling the aquarium slowly and avoiding directing a strong stream of water directly onto the substrate will help minimise disturbance.

How much Flourite Black Sand do I need?

The amount required depends primarily on:

• Aquarium length
• Aquarium width
• Desired substrate depth
• Plant selection
• Aquascape design

The 7kg bag provides greater coverage than the smaller 3.5kg pack and is a better starting point when creating a complete substrate bed.

Larger aquariums or aquascapes with deep slopes and elevated areas may require multiple 7kg bags.

Calculate substrate requirements using the aquarium floor dimensions and desired substrate depth, rather than aquarium litre capacity alone.

3.5kg or 7kg Flourite Black Sand?

3.5kg – A practical choice for smaller planted aquariums, nano setups, feature areas or adding to an existing Flourite substrate bed.

7kg – Better suited to larger aquarium footprints, deeper substrate beds and complete planted aquarium setups.

For larger aquariums, multiple 7kg bags may still be required depending on the substrate depth and aquascape.

Frequently asked questions

What is Seachem Flourite Black Sand?

Seachem Flourite Black Sand is a naturally dark porous clay substrate designed specifically for freshwater planted aquariums and aquascaping.

Is Flourite Black Sand an active substrate?

No. Flourite Black Sand is a stable clay-based planted substrate and is not designed to significantly alter aquarium pH like many active aquasoils.

Is Flourite Black Sand good for aquarium plants?

Yes. It is designed specifically for planted freshwater aquariums and provides a stable porous substrate environment for aquatic plant roots.

Does Flourite Black Sand contain nutrients?

Flourite is a mineral-rich clay substrate but should not be considered a complete replacement for aquarium plant fertilisation. Additional nutrients may be required depending on your plants and setup.

Do I need root tabs with Flourite Black Sand?

That depends on the plants being grown and your fertilisation method. Heavy root-feeding plants may benefit from appropriate root fertilisation.

Will Flourite Black Sand change aquarium pH?

Flourite is designed to have minimal impact on aquarium pH, making it useful when you don't want the substrate intentionally altering your water chemistry.

Do I need to rinse Flourite Black Sand?

Yes. Pre-rinsing is recommended to remove loose dust created during transport and handling. Filling the aquarium slowly after adding the substrate can also help minimise cloudiness.

Does Flourite Black Sand need replacing?

Flourite is designed as a long-lasting substrate and does not require routine replacement simply because it has aged.

Can Flourite Black Sand be used as the only substrate?

Yes. Seachem Flourite Black Sand can be used as the complete substrate bed in a freshwater planted aquarium.

Is Flourite Black Sand suitable for shrimp tanks?

It can be used in freshwater shrimp aquariums where its stable water-chemistry characteristics suit the shrimp species being kept. Unlike active aquasoils, it should not be relied upon to create softer or more acidic water.

Need a smaller pack or different planted substrate?

For smaller planted aquariums, consider Seachem Flourite Black Sand 3.5kg.

Prefer a lighter, more natural appearance? Take a look at Seachem Flourite Sand.

Aquaholics Online also stocks a range of planted aquarium substrates and aquasoils for different planted tank and aquascaping requirements.

For general aquarium gravel, sand and decorative substrates, browse our Aquarium Substrate, Gravel & Sand range.