Flourish vs Flourish Excel: nutrients and organic carbon
By Richard James · Manufacturer sources checked · 28 October 2026
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Quick answer
These are different products: Flourish is a nutrient supplement, while Excel is an organic-carbon product. One is not a dose-equivalent replacement for the other.
Choose the intended job
| Bottle | Question to answer |
|---|---|
| Flourish | What nutrient supply does my routine provide? |
| Flourish Excel | Does its organic-carbon application fit this aquarium? |
Excel has its own exceptions
The Excel instructions distinguish initial use/major water changes from subsequent additions. Its FAQ specifically discusses sensitive Anacharis and marimo. Do not turn an algae anecdote into an off-label concentrated spot-treatment instruction, or assume every plant tolerates the same application.
Can it replace injected CO₂?
Seachem states that Excel is not CO₂. A product amount cannot be converted into a dissolved-CO₂ reading by using its millilitres in a pH/KH table. This guide makes no claim that either product guarantees an algae-free aquarium.
Use the exact calculation
Keep the result in context
Use actual water volume and the exact schedule. Do not equate the liquid millilitres with active nutrient mass. Read units and concentration and schedule changes before comparing a daily and weekly routine.
Sources and check scope
Sources checked 28 October 2026. Manufacturer product information and scoped instructions; no independent efficacy or clinical review. This source check was assisted by AI; it is not an independent human expert or veterinary review. Match the exact pack and consult its manufacturer if directions conflict.