Everything You Need To Know About Excel And Liquid Co2, Experiment Results

-Mak-
  • #1
HI guys, I just finished writing a nonprofessional paper on an experiment I did on the effects of Excel/glut products on aquatic plants. I thought it might interest some of you, especially the introduction, and provide some scientific references to the stuff people say.

This is a slightly shortened version with bits cut out of the introduction, results, some other parts as well. You can read the whole thing here:



The Effect of Glutaraldehyde Isomer Polycycloglutaracetal on the Health and Rate Aquarium Plant Growth

Abstract

An isomeric form of glutaraldehyde is used in planted aquariums due to its reported carbon supplementing properties. Its primary purpose, however, is a biocide for destroying microorganisms in medical and industrial applications. The toxicity of glutaraldehyde to aquatic animals has been well studied, but its effectiveness as a carbon supplement has not. To test the effect of commercial glutaraldehyde supplements, a controlled experiment was set up and run for 21 days. A commercial glutaraldehyde isomer called Flourish Excel was dosed daily in one tank and the other received no supplementation. At the end of the experiment period, qualitative data on plant growth rate and health was collected. The results indicated that Excel did not improve plant growth for all plant species, and it did not affect the growth in the same way. Hemianthus micranthemoides exhibited differences in vertical growth and horizontal growth between tanks, while Micranthemum tweedieI ‘Monte Carlo’ and Hygrophila corymbosa ‘Siamensis 53’ exhibited greener growth and more plant mass in the control tank. Alternanthera reineckiI ‘Mini’ displayed no differences in growth while Echinodorus grisebachiI showed more growth in the control tank.

Introduction

Glutaraldehyde is a biocide that kills microorganisms through cross-linking proteins on the surface of cells. Cross linking prevents cell permeability (Frayne, 2001) by bonding polymer chains together, in this case cell proteins. Glutaraldehyde is effective against bacteria, fungi, and viruses and is used for a broad range of applications. Its uses include sterilizing heat-sensitive medical equipment, oil drilling pipes, and paper-making equipment (Sano et al., 2004).

While commercially sold “carbon boosting” products for aquatic plants are not made from glutaraldehyde but instead its isomer polycycloglutaracetal, the differences between the two are not well studied. However, due to the lack of studies it should be noted that the isomer may have different properties unknown to the public. A Seachem representative stated online in 2005 that “many years of in house testing and research [show] a tremendous increase in growth similar in nature to that seen when CO2 is used. Polycycloglutaracetal is an isomeric form of glutaraldehyde... however it is less reactive and more easily utilized by plants as a carbon source” (Seachem Forum). No additional information on why polycycloglutaracetal is less reactive and more easily utilized has been released.

Because glutaraldehyde is a biocide and its isomer polycycloglutaracetal has displayed similar properties (as an effective algaecide against common aquarium algae), the question about how commercial solutions such as Seachem Flourish Excel can supply “bioavailable organic carbon” has been raised repeatedly by hobbyists. Seachem’s webpage for Excel state that Excel provides a compound very similar to photosynthetic intermediates and reduce the need for CO2 in the production of those intermediates. Photosynthetic intermediates listed by Seachem are involved in the Calvin cycle of photosynthesis. According to a review of the ecotoxicity of glutaraldehyde, under aerobic conditions glutaraldehyde is in fact metabolized to glutaric acid and then to CO2 (Leung, 2001a). Since CO2 is a requirement for photosynthesis, the metabolization of glutaraldehyde in aerobic conditions does have the potential to boost growth through liquid supplement dosing. The major issue is that it is not quantitatively known how much CO2 glutaraldehyde can provide through metabolization.

The aI'm of this experiment was to qualitatively observe the effect of polycycloglutaracetal use in a controlled setting.

Materials

- 2x standard 2.5 gallon tanks
- Chihiros A-series - 45 cm
- UP Aqua Sand substrate - 4 liters
- 2x Azoo Mignon 60 filters
- 250 mL unopened bottle of Seachem Flourish Excel
- Apogee MQ-510 PAR meter
- Aquatic plants:
  • Micranthemum tweedieI ‘Monte Carlo’
  • Hemianthus micranthemoides
  • Alternanthera reineckiI ‘Mini’
  • Hygrophila corymbosa ‘Siamensis 53B’
  • Echinodorus grisebachii

Methods


Setup:

Two standard 2.5 gallon talks were placed next to each other so that their longer sides faced each other. A 45cm Chihiros A series light was placed over the center of both tanks so that each received the same amount of light. The dimmer was set to level 4 out of 7, with 1 being the least intense light and 7 being the most intense. At level 4, PAR (photosynthetically active radiation) was measured to be approximately 105 μm at substrate level in both tanks using the Apogee MQ-510 PAR meter. Each tank was filled with two liters of UP Aqua Sand soil, sloped upwards on one side of each tank for optimal root growth of larger plant species.


glut 1.jpg

Aquarium plants were supplied from an aquarium hobby store or personal stock. A mix of emersed adapted and submersed adapted plants were used in order to guage differences in plant response to Excel after CO2 deprivation. Emersed plants were expected to react more negatively to underwater planting than the submersed plants. It was expected that the addition of glutaraldehyde would not make up for the sudden CO2 deprivation in emersed plants, while it would improve the growth of submersed plants. Species selection encompassed a variety of plant structures, with Echinodorus grisebachiI being a rosette plant, Hygrophila corymbosa ‘Siamensis 53B’ and Alternanthera reineckiI ‘Mini’ being stem plants, and Hemianthus micranthemoides and Micranthemum tweedieI ‘Monte Carlo’ being runner plants. In addition, plant species were selected in order to have variation in CO2 dependency. Micranthemum tweedieI ‘Monte Carlo’ and Alternanthera reineckiI ‘Mini’ are anecdotally though commonly known to have higher CO2 requirements than the other species in order to display optimum growth rate and form.

Micranthemum tweedieI ‘Monte Carlo’ was purchased from an aquarium shop in submersed form. Hemianthus micranthemoides was harvested from personal stock in submersed form. Alternanthera reineckiI ‘Mini’ was harvested from personal stock in emersed form. Hygrophila corymbosa ‘Siamensis 53B’ was harvested from personal stock in emersed form. Echinodorus grisebachiI was purchased from an aquarium shop in emersed form. Each species was purchased or harvested in two portions to split between two tanks.

Each individual plant was planted using aquascaping tweezers. The tanks were then filled to equal levels with dechlorinated tap water. An Azoo Mignon 60 filter was placed on each tank and both were adjusted to the same flow rate.


glut 2.jpg

Dosing/Maintenance:

Glutaraldehyde half-life has been reported to be less than 12 hours in water (Frayne, 2001) and 10.6 hours in river water with sediment (Leung, 2001b). Due to the rapid degradation of glutaraldehyde, newly purchased Seachem Excel was dosed daily at the instructed dose. One tank received the daily Excel treatment and one did not. Each tank also received a twice a week 0.5 mL dose of Nilocg Thrive, a commercial aquarium plant fertilizer based on the Estimative Index dosing method. Nilocg GH booster was dosed to maintain a general hardness of 6 degrees in each tank.

A weekly 30% water change was done to reduce organics and avoid fertilizer buildup. No livestock was added in order to control for potential CO2 produced by respiration.

Results

As predicted, the submersed plants adapted to the experimental tanks better than the emersed plants. The emersed plants exhibited melting of most lower leaves. The submersed plants displayed minor melting of lower leaves, but no shedding. Each plant recovered from melting and displayed signs of new growth by the conclusion of the experiment.


IMG_2255.JPG
IMG_2256 2.JPG

IMG_2259.JPG
IMG_2260 2.JPG
Post planting, day 21

Contrary to expectations, Seachem Excel did not have an immediately observable benefit on the growth of the aquatic plants, nor did it alleviate the difficulties plants face when transitioning to submersed growth as CO2 gas would have done.

See additional plant analysis in full paper

Diatom algae was never cleaned off the glass throughout the 3 week experiment period. Due to Excel’s biocidal properties, once algae started to appear, it was predicted that algae growth would be stronger in the non-Excel tank. The heavier growth of algae in the Excel dosed tank indicates that there was a possible error in the experiment, because algae growth should have been less due to Excel’s biocidal properties.

Discussion

Through the experimental process, it has been shown that Seachem Excel did not provide significant benefits for aquatic plant growth and cannot serve as a replacement for injected CO2. Contrary to the manufacturer's claims, in a home aquarium setting glutaraldehyde, or Seachem’s isomer polycycloglutaracetal, does not appear to drastically improve plant growth.

Variations of this experiment can be used for future trials, such as using all submersed plants in the beginning or adding a third tank with pressurized CO2 injection as an example of optimum growth. More trials need to be conducted in order to lend consistency to the results. Greater sampling sizes and more plants should also be used to reduce dependency on a small set of data.

Personal tanks that receive doses of Excel daily or near-daily have plants that put out healthy new growth. However, as these tanks are not controlled experiments, the positive growth cannot be attributed to Excel with certainty.

Pictures below are an example of a personal display tank. All plants are generating new and healthy growth. With injected CO2 in addition to Excel, species such as Micranthemum tweedieI ‘Monte Carlo’ and Alternanthera reineckiI ‘Mini’ have far better growth rates and form than in the controlled experiment. There has been no melt, excessive algae, or death in any plant, some of which were issues seen in the Excel-dosed tank during the controlled experiment. It can then be reasonably inferred that these symptoms were not caused by Excel during the experiment. Excel simply did not alleviate nor significantly improve pre-existing plant health issues that arose from CO2 deprivation.


Tank small.jpg
Day 15 cut.jpg

References

In the full paper - there are some interesting sources here if you want more information on the mechanisms of glut and its effects on aquatic organisms


I hope this was informative. I will be doing more trials since the sample size for this one was very small. Room for error and such. I wish we had more info on polycycloglutaracetal since Excel is not really glutaraldehyde, but it doesn't seem like Seachem is going to spill. I welcome any feedback and discussion!
 
Giul
  • #2
You did such a nice job formatting this article, it brought me back to my college days!

My question is when did you dose the Excel? I’m not sure if it’s true or not but I was told that you would ideally dose it shortly after the lights are turned on so that it has the maximum amount of time to be absorbed by the plants. IF this is true then the time the Excel was does may influence its effect. I’ve never tested this but it makes sense that the plants need light to absorb nutrients.

My other comment would be I think next time you should extend the experiment (or use larger plants) so that you can physically measure the growth. If you have two established plants that are say 5 cm in height, then you can compare their growth based on their height. It’s easier than counting leaves and more reliable than comparing the plant growth based on observation.

Again, job well done!
 
bitseriously
  • #3
Solid work -Mak- !
You mention possible future trials. What do YOU think would be the setup or factor where a positive growth response would be observed?
Are there plants that are better candidates than others to show a +ve response?
Would a longer duration maybe elicit a response?
Higher dose?
In other words, let’s say you only wanted a setup that would pick up a +ve effect of glut (isomer), how would you go about that?
Also were you surprised to see basically no effect of glut in your trial?

If I may offer one suggestion? You’ve done a good job of creating a treatment and a control environment, but short of an array of tanks running into the dozens, I think your results/finding/conclusions will have more power if you cut back further on the number of variables in play. Go with 1 or 2 types of plants per trial, at most.
Another option (oops two suggestions) is a single tank, with treatment running after control. Set up tank, run it for 2-4 weeks basically to reach some level of stability, use your own plants only to avoid acclimation issues. What you’d be looking for is a leveling off of growth/health parameters for a period of time before you can say your setup is running as a control. Then for another say 3 weeks record your key variables, then after you have that baseline control data, simply start dosing glut. And run for the same duration and measure the same variables. If you see a response, you can even end by removing the glut dosing, and check for a return to baseline.
So exciting!!
 
-Mak-
  • Thread Starter
  • #4
You did such a nice job formatting this article, it brought me back to my college days!

My question is when did you dose the Excel? I’m not sure if it’s true or not but I was told that you would ideally dose it shortly after the lights are turned on so that it has the maximum amount of time to be absorbed by the plants. IF this is true then the time the Excel was does may influence its effect. I’ve never tested this but it makes sense that the plants need light to absorb nutrients.

My other comment would be I think next time you should extend the experiment (or use larger plants) so that you can physically measure the growth. If you have two established plants that are say 5 cm in height, then you can compare their growth based on their height. It’s easier than counting leaves and more reliable than comparing the plant growth based on observation.

Again, job well done!
Yep, right before or as lights turn on is when I dosed, just so that it was fresh when the plants started using it, otherwise it would start degrading before the plants could really get to it!

Thank you for the feedback. I was limited by tank size, though the swords just didn't fare well at all throughout the entire thing. Not sure why. I think the future I may stick to one species with more individual plants and measure the height before and after planting, then calculate average growth.

Solid work -Mak- !
You mention possible future trials. What do YOU think would be the setup or factor where a positive growth response would be observed?
Are there plants that are better candidates than others to show a +ve response?
Would a longer duration maybe elicit a response?
Higher dose?
In other words, let’s say you only wanted a setup that would pick up a +ve effect of glut (isomer), how would you go about that?
Also were you surprised to see basically no effect of glut in your trial?

If I may offer one suggestion? You’ve done a good job of creating a treatment and a control environment, but short of an array of tanks running into the dozens, I think your results/finding/conclusions will have more power if you cut back further on the number of variables in play. Go with 1 or 2 types of plants per trial, at most.
Another option (oops two suggestions) is a single tank, with treatment running after control. Set up tank, run it for 2-4 weeks basically to reach some level of stability, use your own plants only to avoid acclimation issues. What you’d be looking for is a leveling off of growth/health parameters for a period of time before you can say your setup is running as a control. Then for another say 3 weeks record your key variables, then after you have that baseline control data, simply start dosing glut. And run for the same duration and measure the same variables. If you see a response, you can even end by removing the glut dosing, and check for a return to baseline.
So exciting!!
Good questions. I think the H. micranthemoides aka pearled is a good candidate, it doesn't have a strong melting response and it grows like a weed, like the name.
For a setup that would display only the effect of glut, literally every other factor has to be controlled which I recognize is extremely difficult in a non laboratory setting.
Not surprised to see no effect, I think the standard dose is not enough to see improvement. Mostly I think this experiment shows that while CO2 would have massively improved growth, glut didn't and therefore is not a substitute.

Thanks for the suggestions. I think now that I've seen the responses, I can narrow the species selection down to just a couple, like I told Giul.
And the baseline is a really good idea! I think that may have been a large hinderance with this trial. I will definitely do some growing out, trimming, and then start the dosing in the future.
 
Jack B Nimble
  • #5
I have a small plant only tank to grow out some samples and used flourish excel and did nothing to grow plants or kill any algae in there. I over dosed even for a few weeks and nothing. I think it's not a worthy purchase.
 
Vishaquatics
  • #6
I like this study because I've had the same experience in the past. Seachem Excel really does not make a noticeable difference in the planted tank. For me, it was simply another bottle in the cabinet that made an unnoticeable impact on my plants. This study simply confirmed my suspicions. Thank you
 

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