Flourish Excel Dosing Calculator

Precisely calculate the optimal dosage of Flourish Excel for your planted aquarium based on tank size, plant density, and CO₂ supplementation.

Comprehensive Guide to Flourish Excel Dosing for Planted Aquariums

Flourish Excel by Seachem is a popular liquid carbon supplement used in planted aquariums to provide an alternative carbon source for aquatic plants. Unlike traditional CO₂ injection systems, Flourish Excel contains glutaraldehyde, a liquid carbon compound that plants can metabolize. This guide will explore the science behind Flourish Excel, proper dosing techniques, and how to integrate it into your aquarium maintenance routine for optimal plant growth.

Understanding Flourish Excel and Its Mechanism

Flourish Excel’s active ingredient is glutaraldehyde (1.5% concentration), which serves multiple purposes in the planted aquarium:

• Carbon Source: Plants can metabolize glutaraldehyde as a carbon source, though less efficiently than CO₂
• Algae Control: Glutaraldehyde has algicidal properties, particularly effective against green water and thread algae
• Plant Growth Stimulation: The compound appears to stimulate certain metabolic pathways in plants

Scientific Basis of Glutaraldehyde in Aquariums

A study published in the National Center for Biotechnology Information (NIH) demonstrates that glutaraldehyde can be metabolized by certain aquatic plants through alternative carbon fixation pathways. However, its efficiency is approximately 30-40% that of CO₂ gas.

Optimal Dosing Strategies

The calculator above provides personalized recommendations, but here are general guidelines:

Tank Size (gallons)	Plant Density	CO₂ Status	Recommended Initial Dose (mL)	Maintenance Dose (mL)
10-20	Low	None	1.0	0.5 daily
20-50	Medium	None	2.5	1.0 daily
50-100	High	None	5.0	2.5 daily
10-20	High	With CO₂	0.5	0.25 every other day

Integration with CO₂ Systems

When using Flourish Excel alongside injected CO₂, several factors must be considered:

1. Reduced Dosage: With adequate CO₂ (20-30 ppm), Excel dosage should be reduced by 50-70% to avoid glutaraldehyde toxicity
2. Timing: Dose Excel during periods of low CO₂ (typically at night when plants aren’t photosynthesizing)
3. Monitoring: Watch for signs of stress in sensitive species like Vallisneria or Cryptocoryne

CO₂ vs. Excel Comparison

Factor	CO₂ Injection	Flourish Excel
Carbon Availability	High (direct CO₂)	Moderate (metabolized glutaraldehyde)
Plant Growth Rate	Very High	Moderate
Algae Control	Indirect (via plant health)	Direct (algicidal properties)
Equipment Cost	High ($100-$500+)	Low ($10-$20/bottle)
Maintenance	High (equipment, refills)	Low (simple dosing)
pH Impact	Significant (lowers pH)	None

Safety Considerations and Potential Risks

While generally safe when used as directed, improper Flourish Excel dosing can lead to:

• Fish Stress: Some species (particularly scaleless fish and shrimp) are sensitive to glutaraldehyde
• Plant Damage: Overdosing can cause melting in sensitive plants like mosses and some stem plants
• Biofilter Impact: High concentrations may temporarily reduce beneficial bacteria populations

According to research from Iowa State University College of Veterinary Medicine, the LD50 for glutaraldehyde in aquatic organisms ranges from 5-15 ppm depending on species, which is significantly higher than recommended dosing levels (1-3 ppm).

Advanced Application Techniques

For experienced aquarists, these advanced methods can enhance Excel’s effectiveness:

1. Spot Treatment: Use a pipette to apply Excel directly to problem algae areas (1:1 mixture with water)
2. Water Change Timing: Dose immediately after water changes when glutaraldehyde concentration is lowest
3. Combination Therapy: Pair with hydrogen peroxide (3% solution, 1 mL/10L) for stubborn algae outbreaks
4. Gradual Introduction: For sensitive tanks, start with 25% of recommended dose and increase gradually

Troubleshooting Common Issues

Problem: Plant Melting

• Reduce dosage by 50%
• Increase water circulation
• Perform 30% water change
• Check for sensitive species (e.g., Cryptocoryne)

Problem: Fish Gasping

• Immediate 50% water change
• Discontinue Excel for 1 week
• Increase aeration
• Test water parameters

Problem: No Visible Effect

• Verify expiration date
• Check storage conditions (cool, dark)
• Increase dosage by 25% gradually
• Combine with manual algae removal

Long-Term Maintenance Protocol

For sustained success with Flourish Excel:

1. Weekly Testing: Use a glutaraldehyde test kit (if available) or observe plant/fish responses
2. Dose Consistency: Maintain regular dosing schedule (same time daily)
3. Water Changes: Perform 25-30% weekly water changes to prevent accumulation
4. Record Keeping: Log doses and observations to track effectiveness
5. Seasonal Adjustments: Reduce dosage in winter when plant growth slows

Expert Recommendations

The U.S. Fish & Wildlife Service recommends that aquarists using chemical treatments:

• Maintain detailed records of all chemical additions
• Quarantine sensitive species before introduction
• Use activated carbon in filtration when not dosing
• Consult species-specific sensitivity data

Alternative Liquid Carbon Products

While Flourish Excel is the most popular, several alternatives exist:

Product	Active Ingredient	Concentration	Dosing (per 10 gal)	Notes
Flourish Excel	Glutaraldehyde	1.5%	1-2 mL	Most widely available
EasyCarbo	Glutaraldehyde	1.5%	1-2 mL	Similar to Excel, European brand
Metricide	Glutaraldehyde	2.5%	0.6-1.2 mL	Medical grade, stronger concentration
Bio CO₂ Booster	Polycycloglucans	N/A	2-3 mL	Non-algicidal carbon source

Frequently Asked Questions

Q: Can I use Flourish Excel with shrimp?

A: While many aquarists successfully keep shrimp with Excel, it’s recommended to:

• Start with 25% of normal dose
• Use in well-planted tanks (plants absorb glutaraldehyde)
• Monitor closely for signs of stress
• Consider shrimp-safe alternatives for sensitive species

Q: How long does Flourish Excel remain active in the aquarium?

A: Glutaraldehyde degrades over time through:

• Plant uptake (24-48 hours)
• Microbial breakdown (48-72 hours)
• Water changes (immediate reduction)

For this reason, consistent daily dosing is most effective.

Q: Can I mix Flourish Excel with other fertilizers?

A: Yes, but with these precautions:

• Don’t premix with iron supplements (may cause precipitation)
• Dose at different times from water conditioners
• Avoid combining with hydrogen peroxide (same day)
• Test small amounts first in sensitive tanks

Conclusion and Best Practices

Flourish Excel remains one of the most effective tools for planted aquarium enthusiasts, particularly those unable or unwilling to implement CO₂ injection systems. The key to success lies in:

1. Starting with conservative doses and increasing gradually
2. Maintaining consistency in application
3. Monitoring plant and animal responses closely
4. Combining with proper lighting and nutrient balance
5. Using the calculator above to determine precise dosing

Remember that while Flourish Excel can provide significant benefits, it is not a substitute for proper aquarium maintenance. Regular water changes, appropriate lighting periods, and balanced nutrient levels remain the foundation of a successful planted aquarium.