Seachem Flourish Excel Review

One of the first decisions that have to be made for someone planning a planted aquarium is ‘high tech’ or ‘low tech’.  These terms tend to include aspects of plant keeping, including lighting, fertilizers, and selection of plants (low-light plants or high-light plants).  In my mind, the defining factor of a ‘high tech’ planted aquarium is adding a pressurized CO2 system.  I quickly decided there were many disadvantages to attempting a CO2 setup for my first attempt at a planted aquarium, so a low-tech approach became my focus.

Despite all the advantages of a low-tech approach, wouldn’t it be great to have a compromise between an all-in CO2 setup and a slow growth setup? There is such a solution, and it involves a product from Seachem called Flourish Excel.

Seachem Excel Flourish 500ml Bottle

What is Seachem Flourish Excel:

Seachem Flourish Excel is an additive for planted aquariums that is an alternative to gaseous CO2 injection.  It is a liquid you add to your aquarium daily that becomes a carbon source for your plants.  There are limits to how effective this alternative carbon source is – plants are much more efficient in absorbing gaseous CO2 added to the water.  The chemical form of Seachem Excel is more difficult for plants to utilize, so plant growth will be limited compared to traditional CO2.  From the Seachem Website:

“Flourish Excel™ is a source of bioavailable organic carbon. All plants require a source of carbon. This is typically obtained from CO2, but, may also be derived from simple organic compounds (such as photosynthetic intermediates).”

“The reason plants need CO2 is to produce longer chain carbon compounds also known as photosynthetic intermediates. Photosynthetic intermediates includes compounds such as ribulose 1,5-bisphosphate, and 2-carboxy-3-keto-D-arabinitol 1,5 bisphosphate. Although the names are complicated, the structures are quite simple (5 carbon chains). Flourish Excel™ does not contain these specific compounds per se, but one that is quite similar. By dosing with Flourish Excel™ you bypass the involvement of CO2 and introduce the already finished, structurally similar compounds. It is in its structural similarity that Flourish Excel™ is able to be utilized in the carbon chain building process of photosynthesis.”

Seachem Excel is also known as an algaecide.  It is the preferred method for many people to kill off Black Beard Algae (BBA) by using the full-day dosage distributed right on the spot of algae using a pipette.

How to Dose and use Seachem Flourish Excel:

Seachem Excel is to be dosed every day.  One disadvantage to this product is that it has a short half-life of around 12 hours.  This means it won’t hang around in your aquarium for more than a day and, therefore, must be added daily.  It is best to put the daily dose of Excel into your aquarium before the light-on phase starts, which will be in the morning for most people.

Keeping plant growth balanced against algae will always require keeping three things in sync: lighting, nutrients, and CO2.  If either CO2 or nutrients are limited, the result will be algae (if there is excessive light).  It is important to remember that as you increase CO2 by adding Excel, you may need to increase the fertilizers you add to the water column to stay in sync.  You can also consider that you may be able to increase the lighting, either intensity or duration, to match the CO2 being provided.

Seachem offers two dosing scenarios for Excel.  The first is your daily dosing.  They suggest dosing at a rate of 1 capful (5 ml) for every 200 liters of water.  The second is an initial dose (first use or after a long time since any dosing) or following a major (greater than 40%) water change.  For this scenario, Seachem suggests dosing one capful (5 ml) for every 40 liters.

Seachem’s use of ‘capful’ in their instructions is challenging for nano aquarist.  The dosing for very small tanks is best measured using more accurate methods.  I utilize drops as measurement for dosing in a Fluval Spec V.

I have created a dosing calculator that is very handy to determine how much Flourish Excel to add in either scenario (Daily or Water Change). In addition, I created two tables showing the dose suggested in Seachem’s instructions.  Here is the table for daily dosing:

Seachem Excel Daily Dosing Table

For use in my Spec V, I put in 10 drops every morning before I go to work.  Quick and easy, and the results in plant growth and algae control are well worth it!

Below is a table for the dosing required after a major water change:

Seachem Excel Dosing Table for After a Water Change

I have read the reasoning for why this larger dose is recommended.  It seems that a large water change will remove large quantities of residual Excel and CO2.  This increased dosage is an effort to make up for what is removed.  I have chosen not to perform this increased dosage after a water change.  I ignore the instructions and simply continue to perform the daily dose every day.  I know Seachem understands what they are instructing their customers to do.  However, I can’t ignore the very short half-life of Excel, and I don’t fully believe there could be that much CO2 accumulated before a water change.

Cautions for using Seachem Excel:

Most negative things I hear about Excel involve people complaining that it has harmed or killed shrimp in their aquariums.  I have not noticed any problems with my red cherry shrimp.  They are breeding like crazy and quite active and show no adverse effects.  Plant growth is very good, with no detrimental effects from using Excel.

I think most people’s problems with Seachem Excel come from overdosing.  It is important not to rely on ‘capfuls’ or other such measures when dosing on a smaller aquarium.  Get yourself an accurate syringe or dose using drops.

Note that this product is unsuitable for certain plants and will kill them.  This includes mosses,  Vallisneria (Val), and ferns.  If your aquascape includes plants in these categories, avoid using Excel or proceed slowly and with caution.

How Much Does it Cost to Use Seachem Flourish Excel:

One of the concerns about using Flourish Excel when I was planning was whether it would be worth the expense to commit to dosing Excel every day.  I took a close look at the cost, and what I found was surprising.  See the summary table below:

Seachem Excel Cost per year table

For use in a 5-gallon aquarium, the annual cost of using Excel is about $6.50 UDS per year.  I think this is extremely affordable, considering the benefits received.  It’s clear that it is very affordable for nano aquariums.  Where diminishing returns kick in is for larger aquariums.  Dosing a 55-gallon aquarium would cost about $63 USD a year.  Over time, this would probably exceed the cost of filling up CO2 tanks.  The cost tipping point will vary based on goals and expectations, but Excel currently fits my needs.  If I were building another planted tank, I would consider a larger aquarium and would probably favor going with injected gaseous CO2.

Seachem Flourish Excel 500 ml bottle

Seachem Flourish Excel is sold in the following sizes: 100 ml, 250 ml, 500 ml, 2 liters, 4 liters, 20 liters.  The 500 ml bottle is a sweet spot for price and was the best deal for me.

Overall Impressions of Seachem Flourish Excel:

I think it’s a great product and I wouldn’t hesitate to recommend for a nano aquarist who wants to improve plant growth.  The cost is almost negligible in the long term when considering all the benefits to a planted aquarium.  The only sacrifice is remembering to be consistent and dose every day.

18 thoughts on “Seachem Flourish Excel Review

  1. HI,
    HAVE BEEN USING SEACHEM FLOURISH EXCEL FOR OVER A YEAR I HAVE A 300 LITRE AQUARIUM HEAVY PLANTED , I HAVE CRYPTOCORYNE PLANTS AMAZON SWORD ECHINODOROUS RED SENNA, HAVE INCREASED DOSAGE TO 40ML A DAY BEFORE LIGHTS GO ON, SOME AMAZON SWORD LEAVES LOOK PALE AND WORN, HAVE DISCUS FISH , SO HAVE TO BE CAREFUL ON DOSING , IT RECOMMENDS JUST ONE CAP FULL FOR 200 LITRES SO I AM WAY OVER DOSING AT 40ML AT LEAST YOU WOULD OF THOUGHT, BUT SOME PLANTS STILL SEEM TO BE SUFFERING HAVE T5 TUBES 2 PLANT AND 2 DAYLITE ALSO PLANT ROOT TABS HAVE BEEN ADDED ANY SUGGESTIONS WOULD BE WELCOME REGARDS
    STEVE

      1. if i am dosing 40ml with out any results on plants should i up the dosage

  2. Thank you for the review!
    I’ll start using Flourish Excel today too see how it works!
    Greetings from Brasil

  3. I have a 30 gallon deep tank and I am dosing 1ml per gallon which is 3ml every morning. why do they not use that formula for people to know without a doubt. this capful per 50 gallons don’t tell you anything.

    1. 1ml per 10 gallons.

      This works for me in 2 tanks. I have emailed seachem to ask if they could simplify the dosing equation, but no answer.

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