# Flourish excel vs. airstone



## Millipede (Feb 11, 2009)

i just set up a tank with a bunch of plants and was wondering what the effect an airstone has on the levels of CO2 in the water. i was thinking of getting some seachem flourish excel to give my new plants a boost and was also wondering how beneficial that may be if i have and airstone/undergravel filter going full blast


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## singolz (Oct 27, 2011)

there are millions of threads on this. the search function is your friend. to answer your question though, it's not beneficial at all to your plants, the O2 will rid of the CO2 in the water. people here normally only use an aerator at night so that way the fish don't suffocate while the plants aren't photosynthesizing. 
I've read about bad things with an undergravel filter. especially with stem plants. 
also, overdosing excel can be detrimental to your plants as well. it can kill them, so if you are injecting CO2 as well as dosing excel, be a little cautious. good luck to you


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## tapscrew (Jul 1, 2006)

Excel gives a great boost to the plants if they are growing well, just follow the dosing on the bottle, if you over dose it kills off some algaes, I have dosed 5 times the recommended rate to kill algae, some plants like vallisneria will die off but it depends on the species. I belive undergravel filters are not plant friendly, and airstones will drive off CO2 which your plants need to photosynthesise, if they are not growing well adding excel wont help them!


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## Seattle_Aquarist (Mar 7, 2008)

Hi Millipede,

Try it and see; in theory with aeration the CO2 level in the aquarium should reach the same CO2 level as the air, or about 4%.

As for undergravel filters I am afraid I disagree with the consensus. I use undergravel (UG) filters with the following results. Note the crypts and Blyxa in the 45 gallon and the P. stellatus and other stem plants in the 30 gallon. Now they might grow even better without the UG, but I worry about aerobic areas in the substrate so I use a UG.

45 Gallon with UG Filter









30 Gallon with UG filter


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## aquabillpers (Apr 13, 2006)

Since Excel does NOT add CO2 to an aquarium, I don't think the use of an airstone would cause any problems. There would be no CO2 to outgas.

Excel adds carbon via a liquid carrier; CO2 adds it via a gaseous carrier.

It's the carbon, not the carrier.

Bill


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## HeyPK (Jan 23, 2004)

The percent CO2 in air is around 0.03%, and so aeration alone isn't going to give the plants very much CO2.


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## l33tgeist (May 8, 2011)

Re: CO2 level in air, HeyPK's "about 0.03%" is correct. When you hear people talking about climate change, they're all concerned that the CO2 level in the atmosphere is up to 350 parts per million, or 0.035%, which is higher than it used to be.

SeattleAquarist's 4% figure is closer to the CO2 level in air breathed out by a human. If the general atmospheric CO2 level were 4%, Earth would look a lot more like Venus than it does.

You might notice that 350 ppm in the atmosphere is far higher than 30 ppm that people aim for with CO2 injection; why don't they just aerate more? In fact, the concentration of dissolved CO2 in water at equilibrium with the atmosphere is a little under 0.5 ppm. This becomes less confusing when you consider that "ppm" is by weight, and water is about 800 times as dense as air. 350 ppm of CO2 in air becomes less than 0.5 ppm in water because water is much heavier than air.

Heavy aeration will just serve to bring the water CO2 concentration closer in line with the atmospheric CO2 concentration, or about 0.5 ppm CO2 in water. 

The action of Excel (gluteraldehyde) as a plant fertilizer is a bit mysterious, but I don't see any evidence to make me believe that aeration would dispel any of it from the water or reduce its efficacy.


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## singolz (Oct 27, 2011)

aquabillpers said:


> Since Excel does NOT add CO2 to an aquarium, I don't think the use of an airstone would cause any problems. There would be no CO2 to outgas.
> 
> Excel adds carbon via a liquid carrier; CO2 adds it via a gaseous carrier.
> 
> ...


couldn't agree more. I was referring to the co2 already being provided in the aquarium (fish respiration, tap water, etc) not the excel. sorry for the confusion

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## Jessy2363 (Aug 27, 2015)

I see this is a flaming old post but I stumbled across it in google so may as well comment. 
From my experience plants love Oxygen near the roots but hate it touching their leaves in an aquarium situation. So IMO an under gravel air stone would be amazing for growth! But not an airstone where the bubbles run through the leaves driving away Co2.


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## tiger15 (Apr 9, 2017)

There are many misleading info on CO2 in this thread. Let's get the facts straight.

The current atmospheric CO2 concentration is around 400 ppm by volume. The pre industrial concentrations was below 300 ppm by volume.

https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth's_atmosphere

400 ppm by volume in air is equivalent to 775 mg/m3 or 0.775 mg/l by weight in air based on the following complex conversion formula and that 1 m3=1000 l.

http://www.lenntech.com/calculators/ppm/converter-parts-per-million.htm

The solubility (saturation concentration) of CO2 is very high or 1450 mg/l at 25C. But the concentration of CO2 in water is restrained by the concentration of CO2 in air as determined by Henry's law constant.

https://en.wikipedia.org/wiki/Henry's_law

At 25C, the dimensionless Henry constant is 0.83, meaning that if the atmospheric CO2 is 0.775 mg/l by weight, the equilibrium concentration in water is 0.775*0.83 or only 0.64 mg/l by weight.

So bubbling air into the tank water can at best bring the CO2 concentration up to 0.64 mg/l, but more likely to bring down the concentration because fish and microbes generate CO2 in water above and beyond the equilibrium concentration. Since Henry Law applied to pure water only, actual equilibrium concentration of CO2 in non-dosing tank water will vary slightly due to partial pressure of other gases, pH and KH factors. Bubbling pure CO2 into water can drastically increase the CO2 concentration due to high solubility of CO2 (1450 mg/l at 25C) and if it is not restrained, can kill your fish.

It's very important to compare the concentrations in the same unit as many people have mixed up ppm by volume (conventionally cited for air) with ppm by weight in water. They are apple and orange comparison and I have discussed this in another thread. http://www.aquaticplantcentral.com/...-discussions/133058-diy-co2-2.html#post928778


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## tiger15 (Apr 9, 2017)

aquabillpers said:


> Since Excel does NOT add CO2 to an aquarium, I don't think the use of an airstone would cause any problems. There would be no CO2 to outgas.
> 
> Excel adds carbon via a liquid carrier; CO2 adds it via a gaseous carrier.
> 
> ...


I am not certain how excel works as a liquid co2 source as I can't find any scientific literature to support it. But there is plenty of data to support that excel is an effective algacide at just 1 to 2 ppm, and that excel, or its generic name glutaldehyde, has a half life of about 10 hours decaying into h2o and co2. So excel can add co2 to water by natural decay if it hasn't been extracted directly by photosynthesis.


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## jrIL (Apr 23, 2005)

I can tell you that I have seen positive results from using excel. Not as good as co2 but it helps.


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## Midlifecrisis (Aug 13, 2017)

Glutaraldehyde is excellent but not as a source of CO2. One 1ml of FE contains approximately 15 mg glutaraldehyde (1.5%?). When that is metabolized into CO2 and H2O The quantities produced are tiny. One ml of FE is suggested for 50 liters of water. That would generate micrograms of CO2. I believe it works as an algaestatic. I have no doubts that it works, though. I use it in my low tech tank which is quite dense w plants. And no signs of algae


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