# Why Does Flourish Excel Kill Algae?



## ETK

Anyone know why Flourish Excel kills algae?

Once I got my CO2 in balance with my light and fert levels, I found that excel was very effective at killing off the stubborn BBA and a little hair algae that had stopped growing, but wouldn't go away. That is great, but it bothers my that I don't know why.

I hesitated to use excel at all since I am also not really clear why adding another source of carbon (which is what it is described as) would be helpful in a tank with injected CO2.

Any thoughts?


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## mr.bigglesworth

Excel is used as a herbicide in large quantities. It will kill plants too if you dose enough.


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## exv152

It's an effective algacide because of its glutaraldehyde content - a disinfectant and preservative chemical used in the medical profession.


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## ETK

exv152 said:


> It's an effective algacide because of its glutaraldehyde content - a disinfectant and preservative chemical used in the medical profession.


Thanks. That seems right based on a web search. Anyone else feel that the marketing of excel is misleading? They seem to be marketing a product as a source of carbon, while one of the main benefits seems to be the direct effect of a disinfectant. I have to admit I like the effects on my aquarium, but I didn't know it contained glutaraldehyde.


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## rickey

Carbon is a by product of the glutaraldehyde when it reacts with organic material in the system. No organic no carbon.

Rickey


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## Seattle_Aquarist

ETK said:


> Thanks. That seems right based on a web search. Anyone else feel that the marketing of excel is misleading? They seem to be marketing a product as a source of carbon, while one of the main benefits seems to be the direct effect of a disinfectant. I have to admit I like the effects on my aquarium, but I didn't know it contained glutaraldehyde.


Hi ETK,

A good question; I think a lot of folks might not understand why Excel / Glutaraldehyde is used as a source of carbon for our aquarium plants. On their website Seachem has the transcript of a complete paper that was that was done in the scientific journals.

Here is an except of that paper:


> The chemical structure of Flourish Excel™ is quite similar
> to some of the products of photosynthesis such as
> Ribulose 1,5-bisphosphate and 2’-carboxy-3-keto-Darabinitol
> 1,5 bisphosphate. Flourish Excel™ possesses
> the same basic 5-carbon chain seen in these molecules.
> The route through which Flourish Excel™ is used by
> plants involves two main processes: a) adsorption and b)
> transformation. Because the active component of Flourish
> Excel™ is charge neutral and of relatively low molecular
> weight it is readily adsorbed directly across the
> cellular membranes of most plants. Once present within
> the cell there are two possible modes of action. It may be
> biologically converted into CO2 and then utilized in that
> fashion. Or, it may be converted into any number of more
> complex organic compounds needed for the life processes
> of the plant (e.g. sugars, starch, amino acids, etc).


There is a good explanation of the Calvin Cycle and how during the Calvin cycle a molecule similar to glutaraldehyde, RuBP (ribulose 1,5 bisphosphate ), is formed naturally which eventually becomes the building blocks for plant growth - glucose, fructose, and starch. The Excel/glutaraldehyde can provide a molecule similar enough to the RuBP molecule that plants can utilize it to create the same glucose, fructose, and starch and thus achieve strong growth.

Here is a good You Tube presentation on the subject:





As to why Excel/Glutaraldehyde is not marketed as algacide is pretty simple, algacides, weed killers, etc are heavily regulated while chemical disinfectants and aquarium supplements are not.


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## DogChristopher

Wow! What great info everybody. I have been wondering these exact same things myself and after taking a biology course last year I actually understood that video! I am going to my LFS today to get some Flourish Excel and some otocinclus!


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## jfynyson

Correction, disinfectants are very much regulated. It simply cost too much to register so it's deemed a preservative in the formula. That way only the the manufacturer of the glut has to register it for use as such under FIFRA regulations, not as an active kill claim.

Sent from my ADR6400L using Tapatalk 4 Beta


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## psalm18.2

I often wonder what the effects of using this product has on fish in the long run.


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## Seattle_Aquarist

Hi psalm18.2,

I have dosed Excel / glutaraldehyde at 1X initial after water changes and 2X daily dose level for over 4 years. I have found no adverse effects with any of the species I keep including more sensitive species such as rainbowfish, Cardinal Tetras, and Apristogrammas. It doesn't seem to effect fertility since I have spawned angels, Corys, and Apistos with no ill effects on parents or fry!

I have learned to dose liquid carbon supplements after doing any necessary 'in tank' maintenance because my arm feels 'ichy' if I put it in the tank after dosing.

Juvies of a spawn Apistogramma cacatuoides 'Triple Red'


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## psalm18.2

Seattle_Aquarist said:


> Hi psalm18.2,
> 
> I have dosed Excel / glutaraldehyde at 1X initial after water changes and 2X daily dose level for over 4 years. I have found no adverse effects with any of the species I keep including more sensitive species such as rainbowfish, Cardinal Tetras, and Apristogrammas. It doesn't seem to effect fertility since I have spawned angels, Corys, and Apistos with no ill effects on parents or fry!
> 
> I have learned to dose liquid carbon supplements after doing any necessary 'in tank' maintenance because my arm feels 'ichy' if I put it in the tank after dosing.
> 
> Juvies of a spawn Apistogramma cacatuoides 'Triple Red'


That's good to know. Thanks.


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## Misant

Seattle_Aquarist said:


> Hi ETK,
> 
> A good question; I think a lot of folks might not understand why Excel / Glutaraldehyde is used as a source of carbon for our aquarium plants. On their website Seachem has the transcript of a complete paper that was that was done in the scientific journals.
> 
> Here is an except of that paper:
> 
> There is a good explanation of the Calvin Cycle and how during the Calvin cycle a molecule similar to glutaraldehyde, RuBP (ribulose 1,5 bisphosphate ), is formed naturally which eventually becomes the building blocks for plant growth - glucose, fructose, and starch. The Excel/glutaraldehyde can provide a molecule similar enough to the RuBP molecule that plants can utilize it to create the same glucose, fructose, and starch and thus achieve strong growth.


I'm at the moment feeling pretty sure that Seachem's claims that glutaraldehyde as an intermediate for either of those two metabolic compounds is pretty much a ginormous load of crap. Everything I've seen online regarding this is pretty much regurgitated from Seachem's page. 

I realize that ribulose 1,5 bisphosphate and glutaraldehyde both have a 5 carbon chain, but those two compounds are significantly different. You don't just find a compound that roughly fits the form of something else and claim that it's a metabolic intermediate for such. Not that 99% of the population would likely ever question it... But I find it a bit shocking how far this "Liquid Carbon" garbage has spread. It's even all over youtube for chrissakes. WTF?

MAYBE, to some very small degree, it's happening. Maybe I'm totally wrong, but I feel like we're being greased with that claim. Anyone have anything solid to show to the contrary? 
If not, I call B.S. but have to admire their marketing tactics.


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## ChemGuyEthan

Found some interesting info about glutaraldehyde on the wiki page and a page posted by the CDC that talks about the mode of action of the compound. It appears that glutaraldehyde in water generates a number of species. The "active ingredient" polycycloglutaracetal appears to be a trade name, but is presumably a polymeric form of the ring-shaped, hydrated glutaraldehyde that can form in water. The anti-algae properties are I'm sure related to glutaraldehyde's properties as a disinfectant, see CDC link. I would think in high enough doses it could also harm plants and possibly fish.

Finally found something useful. In the PDF of this article, they show a figure with a polycyclic form of glutaraldehyde (compound V in figure 1) which naturally occurs with high concentrations in water and upon dilution breaks up. It's likely this is the path Excel takes, once that breaks up, it could be taken up by plants or attack the algae depending on which form it takes in proximity to the organism.

In response to questioning Excel's place in photosynthesis, who knows. I use it and it seems to help. One could argue the cyclic structure is on it's way to being a more complex sugar... They claimed in 2005 that they were going to be filing a patent but I can't find that they ever did, or it wasn't granted as of yet. Perhaps they were unable to prove their claims scientifically. Doesn't mean they're wrong, just they couldn't prove their claim.


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## Zapins

A recent post on this topic was brought up by misant777 and can be read here: http://www.aquaticplantcentral.com/...s-discussions/90962-gluteraldehyde-topic.html

Lots of information there about the mechanism of excel and how it works.


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## plantbrain

Excel like many similar compounds in this group cross link proteins, specifically on the cell wall. Algae have cell walls also.

Does not say WHY there is selectivity.

Generally, smaller organisms are less susceptible to general biocides. Plants seem to detoxify it and gain tolerance to it, even Egeria and Vals over time become immune. Why this is, and has anyone does any radio isotopic pathways in plants and algae, not that I know of.That ain't cheap nor easy.


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## Chris_Produces

Great info here about the Excel. However, I do feel like I just had a years worth of biology and chemistry shoved into my brain and it's now on overload. :confused1:


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