Seachem Flourite Black Sand 3.5kg – Planted Aquarium Substrate

Create a striking foundation for your planted aquarium with Seachem Flourite Black Sand 3.5kg, a naturally porous clay substrate designed specifically for freshwater planted aquariums.

The dark black appearance provides excellent contrast against green and red aquatic plants, colourful fish, shrimp, rocks and driftwood, making it an attractive choice for planted aquariums and aquascapes.

Unlike active aquasoils, Flourite Black Sand is a stable, long-lasting planted aquarium substrate designed to have minimal impact on aquarium pH. This makes it an excellent option when you want a plant-friendly black substrate without deliberately altering your aquarium's water chemistry.

Flourite Black Sand can be used on its own as the complete substrate bed and does not require routine replacement as it ages.

Key features and benefits

• Designed for planted aquariums – Made specifically for freshwater planted tanks and aquascaping.
• Dark black appearance – Creates strong contrast against aquatic plants, fish, shrimp and aquascaping materials.
• Porous clay substrate – Provides a suitable substrate environment for aquatic plant roots.
• Stable and long-lasting – Designed to remain in the aquarium without requiring routine substrate replacement.
• Minimal effect on pH – A useful alternative to active aquasoil when you don't want the substrate 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 gravel or substrate.
• Not chemically coated or treated – A naturally dark porous clay substrate rather than coated decorative gravel.
• 3.5kg pack – Convenient for smaller planted aquariums, nano aquascapes and feature areas.

Product specifications

Brand: Seachem
Product: Flourite Black Sand
Colour: Black
Pack Size: 3.5kg
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?

The substrate colour can dramatically change the appearance of an aquarium.

Flourite Black Sand creates a dark foundation that helps aquarium plants and livestock stand out, making it particularly attractive in heavily planted tanks and detailed aquascapes.

Green plants can appear brighter against the dark substrate, while red plants, colourful fish and freshwater shrimp can provide striking visual contrast.

At the same time, you're getting a substrate designed specifically for planted aquariums rather than choosing black sand purely for its appearance.

Is Flourite Black Sand an aquasoil?

No.

Seachem Flourite Black Sand is better described as a stable porous clay planted substrate.

Many active aquasoils are designed to influence water chemistry by lowering or buffering parameters such as pH and hardness.

Flourite Black Sand is designed to have minimal impact on aquarium pH, making it useful when you want a planted substrate without intentionally changing your water chemistry.

Flourite Black Sand vs active aquasoil

Both can provide excellent foundations for planted freshwater aquariums, but they serve different purposes.

Active aquasoil may be preferable when you specifically want the substrate to influence water chemistry and create softer, more acidic conditions.

Flourite Black Sand is a better fit when you want a stable, long-lasting planted substrate while maintaining greater control over water parameters.

Flourite also does not rely on temporary buffering properties, so it can remain part of an established aquarium substrate bed long term.

Flourite Black Sand vs regular Flourite Sand

The most obvious difference is appearance.

Flourite Black Sand creates a much darker substrate bed and stronger contrast against plants and aquarium livestock.

Flourite Sand provides a lighter, more natural earthy appearance.

Both are porous clay substrates designed for planted freshwater aquariums and are intended to remain stable rather than functioning like active aquasoil.

Choose between them primarily according to the appearance you want to create in your aquascape.

Is Flourite Black Sand good for aquarium plants?

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

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

Successful plant growth also depends on lighting, carbon dioxide availability, fertilisation and the requirements of the individual plant species.

Does Flourite Black Sand contain fertiliser?

Flourite Black Sand is best thought of as a plant-friendly mineral substrate rather than a complete aquarium fertiliser.

The porous clay provides a suitable environment for aquatic plant roots, but it does not eliminate the need for appropriate plant nutrition.

Depending on the plants you're growing and your fertilisation method, root tabs or water-column fertilisers may still be required.

Does Flourite Black Sand affect aquarium pH?

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

This makes it useful when you want the appearance and plant-growing benefits of a specialised planted substrate without intentionally buffering the aquarium toward softer or more acidic conditions.

Always monitor aquarium water parameters according to the needs of the fish, shrimp and plants being kept.

Does Flourite Black Sand need replacing?

Flourite is designed as a long-lasting planted aquarium substrate.

It does not require routine replacement simply because the substrate has aged.

This is particularly useful in established planted aquariums where removing and replacing the entire substrate bed would require significant disruption to 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 it according to your aquascape.

A shallower foreground with greater substrate depth toward the rear can provide additional rooting depth while also creating visual perspective.

Carefully plant aquatic plants into the substrate before filling the aquarium.

When filling, 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 adding the substrate to your aquarium.

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

How much Flourite Black Sand do I need?

The amount required depends on:

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

A 3.5kg bag is particularly useful for smaller planted aquariums, nano setups, foreground areas and feature sections.

Larger planted aquariums or deeper substrate beds may require multiple bags or the larger 7kg Flourite Black Sand pack.

3.5kg or 7kg Flourite Black Sand?

Choose the pack size according to the area you need to cover.

3.5kg – Ideal for smaller planted aquariums, nano aquascapes, feature areas or adding to an existing Flourite substrate bed.

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

For larger aquariums, multiple bags may still be required depending on the desired substrate depth.

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 specifically designed 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 plant fertilisation. Additional nutrients may be required depending on your plants and aquarium 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 my 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. Fill the aquarium slowly after adding the substrate to 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 on its own?

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 larger pack or different planted substrate?

For larger planted aquariums, consider Seachem Flourite Black Sand 7kg.

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

Aquaholics Online also stocks a range of planted aquarium substrates and aquasoils for different aquarium setups.

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