Seachem Flourish Excel 250ml – Liquid Carbon for Planted Aquariums

Seachem Flourish Excel 250ml is a bioavailable organic carbon supplement designed to support healthy plant growth in freshwater planted aquariums.

All aquarium plants require carbon for photosynthesis and growth. While this is commonly supplied through injected CO2, Flourish Excel provides plants with an alternative source of readily available organic carbon.

It can be used on its own in lower-tech planted aquariums or alongside CO2 injection in more advanced aquascapes.

Key Features and Benefits

• Bioavailable organic carbon source for aquarium plants
• Supports healthy planted aquarium growth
• Can be used as an alternative to CO2 injection
• Can also be used alongside injected CO2
• Ideal for low-tech planted aquariums
• Helps support efficient photosynthesis
• Promotes the more easily utilised ferrous form of iron
• Suitable for freshwater planted aquariums
• Easy liquid dosing
• Does not directly alter aquarium pH
• 250ml bottle ideal for regular planted-tank maintenance

What Does Seachem Flourish Excel Do?

Aquarium plants require carbon to build new plant tissue.

In natural and high-tech planted aquariums, much of this carbon comes from dissolved carbon dioxide.

Flourish Excel provides a bioavailable organic carbon source that can be used by aquatic plants during photosynthesis.

This makes it particularly useful for planted aquariums where a complete CO2 injection system is not practical.

Alternative to Injected CO2

Flourish Excel can be used as a simpler alternative to pressurised CO2 injection.

It does not provide exactly the same level of growth that a well-managed CO2 system can achieve, but it can still provide a substantial carbon source for aquarium plants.

It is ideal for:

• Beginner planted aquariums

• Low-tech aquascapes

• Nano planted tanks

• Community aquariums with live plants

• Tanks where installing CO2 equipment is impractical

Can Flourish Excel Be Used With CO2?

Yes.

Flourish Excel can be used alongside injected CO2.

Using both can provide additional carbon availability for aquarium plants without needing to continually increase injected CO2 levels.

This can be useful in more heavily planted aquariums and aquascapes.

How to Dose Seachem Flourish Excel

Initial Dose

On first use or after a major water change greater than 40%:

Use 5ml for every 40 litres of aquarium water.

Regular Dose

After the initial dose:

Use 5ml for every 200 litres daily or every other day.

For smaller aquariums, each thread inside the Seachem cap is approximately 1ml.

Example Dosing

40L Aquarium

Initial dose: 5ml

Regular dose: 1ml

100L Aquarium

Initial dose: 12.5ml

Regular dose: 2.5ml

200L Aquarium

Initial dose: 25ml

Regular dose: 5ml

Always calculate the dose according to your aquarium's actual water volume where practical.

When Should Flourish Excel Be Added?

Flourish Excel can be dosed at any time of day.

Because plants use carbon during photosynthesis, dosing during the aquarium lighting period is a logical choice.

Seachem states that the carbon source can remain available for up to approximately 24 hours.

Flourish Excel Does Not Affect pH Like CO2

Flourish Excel is not carbon dioxide gas.

Because of this, it does not lower aquarium pH in the same way that increasing dissolved CO2 can.

This can make it useful where additional carbon is desired without further reducing pH.

Flourish Excel & Iron

Flourish Excel also has iron-reducing properties.

It helps promote iron in the ferrous Fe²⁺ state, which is more readily utilised by aquarium plants than ferric Fe³⁺ iron.

This makes it particularly useful as part of a broader planted-aquarium fertilisation program.

Flourish Excel & Algae

Some aquarium keepers report reduced algae growth while using Flourish Excel, particularly with some forms of black beard algae.

However, Seachem does not manufacture or market Flourish Excel as an algaecide.

It should not be overdosed or directly applied as a concentrated spot treatment to aquarium plants, as this can cause damage.

Use Flourish Excel only according to the recommended dosing directions.

Suitable Aquarium Plants

Flourish Excel can be used with many commonly kept freshwater aquarium plants including:

• Anubias
• Cryptocoryne
• Amazon Swords
• Rotala
• Bacopa
• Java Fern
• Bucephalandra
• Many stem plants
• Many carpeting plants

Some sensitive plants may require more cautious dosing.

Flourish Excel & Vallisneria

Vallisneria has sometimes been reported as sensitive to excessive Flourish Excel dosing.

Seachem's own testing found that normal maintenance doses were generally tolerated, while higher-than-recommended doses were more likely to cause temporary leaf melting.

For aquariums containing Vallisneria, follow the standard dose carefully and avoid overdosing.

Flourish Excel & Anacharis

Anacharis is particularly sensitive to Flourish Excel.

Seachem recommends dosing every other day rather than daily when Anacharis is present.

Start cautiously with sensitive plants and observe their response.

Flourish Excel for Low-Tech Planted Tanks

Flourish Excel is especially useful in low-tech planted aquariums where you want to improve carbon availability without installing:

• CO2 cylinders
• Regulators
• Solenoids
• Diffusers
• CO2 tubing

It provides a simple liquid dosing option for customers wanting healthier plant growth with less equipment.

Flourish Excel with Other Seachem Plant Products

Flourish Excel can be combined with other Seachem planted-aquarium products depending on plant requirements.

Useful companion products include:

• Seachem Flourish
• Seachem Flourish Tabs
• Seachem Flourish Iron
• Seachem Flourish Potassium
• Seachem Flourish Nitrogen
• Seachem Flourish Phosphorus

Excel primarily supplies carbon, while these other products provide additional nutrients.

Product Specifications

Frequently Asked Questions

What is Seachem Flourish Excel used for?

Flourish Excel provides a bioavailable organic carbon source for freshwater aquarium plants.

Is Flourish Excel liquid CO2?

No. Flourish Excel is not carbon dioxide gas. It provides plants with a bioavailable organic carbon source that can support photosynthesis and growth.

Can Flourish Excel replace CO2 injection?

It can be used as an alternative in many planted aquariums, although a well-managed injected CO2 system can generally provide stronger plant growth.

Can I use Flourish Excel with CO2?

Yes. Flourish Excel can be used alongside injected CO2.

How much Flourish Excel should I use?

On initial use or after a water change greater than 40%, use 5ml per 40 litres. After that, use 5ml per 200 litres daily or every other day.

Does Flourish Excel lower aquarium pH?

No. It is not CO2 gas and does not directly lower pH in the same way injected carbon dioxide can.

Is Flourish Excel an algae treatment?

No. Seachem does not market Flourish Excel as an algaecide. Some aquarists observe reduced algae growth while using it, but it should not be overdosed or used as a concentrated spot treatment.

Is Flourish Excel safe for fish?

Yes. Seachem states that Flourish Excel is safe for fish when used according to directions.

Is Flourish Excel safe for Vallisneria?

Normal maintenance doses are generally tolerated, but excessive doses may cause temporary Vallisneria leaf melting. Avoid overdosing.

Can I use Flourish Excel with Anacharis?

Yes, but Anacharis is particularly sensitive. Seachem recommends dosing every other day rather than daily.

Can I use Flourish Excel with Flourish Tabs?

Yes. Excel supplies organic carbon, while Flourish Tabs provide nutrients directly to plant roots, making them complementary products.