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Low Energy, Water Changes, CO2, Algae, and Pseudoscience.

Tim Harrison

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Reading countless forum threads on low energy setups, water changes, fluctuating CO2 levels and algal blooms, I am amazed and somewhat despairing to discover that a direct and causal relationship between the above factors seems to have worked its way into aquarium folklore to the extent that it is now blindly accepted as actual scientific fact.

There is an underlying philosophy at work here one that pervades many pursuits that are thought to be underpinned by science, and not least is our great hobby (obsession) maintaining a healthy planted tank.

Unfortunately, it is more often than not, pseudoscience and not science that becomes conventional wisdom (accordingly conventional wisdom is often wrong) through nothing more than repeated use and familiarity, and then before too long we find ourselves preaching it as gospel no matter how scientifically implausible an idea it may be.

I think what is really going on is that we tend to associate truth with convenience and not necessarily scientific rigor. It is for example easy to blame the algae explosion in our lower energy tanks on the CO2 spikes supposedly associated with frequent and significant water changes than on poor husbandry.

So although the science behind this theory is convincing I think it is complete and utter nonsense, and for several very good reasons, not least those below.

1. Yes gasses do get compressed in a high pressure environment such as a potable water delivery system (pipes) but where does this supposedly significant increase in CO2 come from once the water exits the tap in our homes?

2. Surely the CO2 content of the water used to top up our tanks will be the same as it was at the beginning - in the reservoir - all that has happened is that the same amount of gas has re-equilibrated at atmospheric pressure?
This is why the “unscrewing the lid on the fizzy pop bottle” analogy is so inappropriate, the levels of CO2 involved are hugely different.

3. So where did all that extra CO2 come from – the extra CO2 that some pundits claim so upsets the balance of our tanks?
Bacteria in the pipes? I hardly think so.

4. For one thing if bacteria were so prevalent in our water supply system, as to make a significant contribution to its CO2 levels during transit, surely we’d all be dying of cholera and typhoid, or at the very least constantly mincing to the toilet with our butt cheeks firmly clenched...well surely we would...wouldn't we?

5. If the levels of CO2 were that high that they are capable of causing algal blooms and other mischief, wouldn’t our fish be gasping at the surface every time we did a water change?

6. Wouldn’t the daily fluctuations due to plant photosynthesis and respiration be of greater significance?

7. And do fluctuating levels of CO2 actually cause algal blooms anyway? Has it ever been proven beyond all reasonable doubt using scientifically rigorous and statistically significant research?

8. And as for all this leaving the water to degas overnight, and doing secret water changes when the algae aren't looking...please do me a favour.

Anyway, I could go on but won’t.

Regardless of the validity of the water change/CO2 theory I tend to think that if other parameters are well balanced a soil substrate/lower energy system should be robust enough to withstand the occasional temporary fluctuation without adverse effects.

Mine obviously is since despite changing 30% - 50% of the water twice a week I haven’t had any algal blooms and what is more I barely have to clean the glass. Check out the photos in the links below if you don’t believe me.

And just to finish, a cautionary note regarding causality, it’s very often not what you think. Take for example the butterfly effect:
Butterfly flaps wings and somewhere there’s a hurricane.

I prefer the alternative scenario:
Pseudoscientist flaps mouth and somewhere there’s a storm in a teacup.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

:thumbup: Now that I understand, having bookmarked your threads for continued future reference I find I get lost/confused by the 'applied science' on what is essentially growing immersed plants.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Troi wrote:
doing secret water changes when the algae aren't looking...please do me a favour.

Spyder wrote:
Can you eloborate on this one please. Don't you have a 2 hour "siesta" period to try and "confuse" your algae?

Tricky little blighters!
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Troi said:
Reading countless forum threads on low energy setups, water changes, fluctuating CO2 levels and algal blooms, I am amazed and somewhat despairing to discover that a direct and causal relationship between the above factors seems to have worked its way into aquarium folklore to the extent that it is now blindly accepted as actual scientific fact.

There is an underlying philosophy at work here one that pervades many pursuits that are thought to be underpinned by science, and not least is our great hobby (obsession) maintaining a healthy planted tank.

Unfortunately, it is more often than not, pseudoscience and not science that becomes conventional wisdom (accordingly conventional wisdom is often wrong) through nothing more than repeated use and familiarity, and then before too long we find ourselves preaching it as gospel no matter how scientifically implausible an idea it may be.
As is often the case, one form of pseudoscience is cleverly used to attack another form of pseudoscience. At the end of the day, a real scientist would use a scientific method to test the validity of conventional wisdom. If anyone really wants to determine whether or not, for example, tap water contains high levels of CO2, why not simply beg, borrow or steal a CO2 meter and measure the tap's CO2 water content? Lacking an expensive meter, the only option left, which is not as accurate, is to measure the pH of the tap water as it exits the faucet and to let the water sit for an hour or so while taking regular pH readings. It will typically be discovered that the pH rises over time. This is attributed to the offgassing of the CO2 and subsequent reduction in Carbonic acid. I say "attributed" because, of course the pH test results do not verify or confirm that loss of Carbonic acid is responsible for the rise in pH. Only a CO2 meter will confirm this.

Troi said:
So although the science behind this theory is convincing I think it is complete and utter nonsense, and for several very good reasons, not least those below.

1. Yes gasses do get compressed in a high pressure environment such as a potable water delivery system (pipes) but where does this supposedly significant increase in CO2 come from once the water exits the tap in our homes?

2. Surely the CO2 content of the water used to top up our tanks will be the same as it was at the beginning - in the reservoir - all that has happened is that the same amount of gas has re-equilibrated at atmospheric pressure?
This is why the “unscrewing the lid on the fizzy pop bottle” analogy is so inappropriate, the levels of CO2 involved are hugely different.

3. So where did all that extra CO2 come from – the extra CO2 that some pundits claim so upsets the balance of our tanks?
Bacteria in the pipes? I hardly think so.
It's unbelieveable to me that people have a difficult time accepting that municipal water supplies are treated with CO2. It's also difficult to understand why the concept of underground bacterial action where ground water comes from, is so difficult to grasp. Am I living on a different planet, or has no one ever gone to a supermarket or restaurant and bought spring water in a bottle? Those bubbles in the bottle are CO2 bubbles. Supposed scientists don't know this? How did the CO2 get there? When we find the answer to that question, we will have an insight into the concept and possibility of groundwater CO2 accumulation. In fact, the high acidity cause by groundwater CO2 accumulation is often responsible for dissolving the calcium carbonate when that water flows through limestone deposits causing the water to dissolve the lime and causing the tap water to be unusually high in hardness.

Stalactites in underground caves is due to CO2 enriched groundwater dissolving the CaCO3. Any organic material through which the water passes prior to reaching the lime deposits will become enriched with CO2 due to microorganism respiration within that sediment.
350px-Labeled_speleothems.jpg


If anyone is unsure as to whether CO2 is added to municipal water supplies, have a look at this typical scheme for gas treatment => http://www.elmemesser.lv/assets/media/2 ... dd6abd.pdf
This gas treatment scheme is not all-encompassing and of course is used depending on the local conditions and water source. In any case this is how it can exist in the tap at higher than atmospheric levels.

Municipal water supplies are often loaded with CO2, because CO2 is used to process the water specifically because the Carbonic acid is a much safer acid to use than other toxic acids. The facility will often raise the pH to precipitate out carbonate salts an then add CO2 to lower the pH. Tap water can contains up to about 50ppm. Again, carbonated spring water is usually found in well water supplies. Since the CO2 is added under pressure, and since the water is then pressurized in order to deliver it to the tap, the CO2 content remains high and remains under pressure. The pop bottle analogy is entirely appropriate even though the concentration of CO2 gas in cola is much higher than in tap water, the principle of higher gas pressure trapped in liquid suddenly escaping as a result of the lowering of the pressure after exiting the supply line is the same and so is entirely appropriate. In a non injected tank the CO2 concentration is around 8ppm, however, there is also an exception. High organic content in soil or leaf sediments produce CO2 as a result of bacterial action in the sediment. The CO2 will then escape the sediment and will be in the water column. There is a possibility therefore that in general the average CO2 concenration level is higher than that in a non organic sediment tank and therefore the CO2 "delta" is not as great when doing a water change. This is a supposition. I do not know the actual values so I cannot say.

Troi said:
4. For one thing if bacteria were so prevalent in our water supply system, as to make a significant contribution to its CO2 levels during transit, surely we’d all be dying of cholera and typhoid, or at the very least constantly mincing to the toilet with our butt cheeks firmly clenched...well surely we would...wouldn't we?
Pathogen treatment is independent of pH treatment.

Troi said:
5. If the levels of CO2 were that high that they are capable of causing algal blooms and other mischief, wouldn’t our fish be gasping at the surface every time we did a water change?
No, that's another pseudoscience tidbit I'm afraid. The speed at which hypercapnia shows it's effects takes longer than the time it takes for the CO2 to dissipate. Additionally, the water change percentage is not usually 100% so the concentration gets diluted but this still has an effect on the plants if they see a significant increase in the available CO2.

Troi said:
6. Wouldn’t the daily fluctuations due to plant photosynthesis and respiration be of greater significance?
No, sorry. More pseudoscience from a low tech perspective. The uptake rate in a non enriched tank is not as quick as in an enriched tank. the equilibrium rate from atmosphere to water modulates the fluctuations. Suddenly dumping large amounts of gas in the tank is different than the minor diurnal variations. Natural variations in CO2 concentration always occur. It is impossible to maintain exactly the same concentration to the nearest molecule, but plants are not affected by these minor variations.

[quote="Troi"7. And do fluctuating levels of CO2 actually cause algal blooms anyway? Has it ever been proven beyond all reasonable doubt using scientifically rigorous and statistically significant research? [/quote]No. There is reasonable doubt. There is only strong correlation. It's easy to test though, but low tech armchair pundits just like to sit around throwing stones at the people who have already resolved the issues. It's very easy to get up off the buttocks, go buy some gas/equipment and intentionally vary the CO2 levels in the tank in order to observe the effects. There are lots of factors affecting CO2 instability, such as lighting, plant mass, temperature, mean daily baseline levels, flow and distribution and so forth, so in order to find correlation, one has to be able to freeze the values of all variables in order to detect the effcts of one variable.


Cheers,
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

It's easy to test though, but low tech armchair pundits just like to sit around throwing stones at the people who have already resolved the issues.

Woah Clive...it was only meant as a bit of light-hearted philosophy, but thanks for the detailed explanation anyway; even though you went off piste a bit it was still very interesting.

Here's what I found out...If the water is acidic (lower than 7), lime, soda ash, or sodium hydroxide is added to raise the pH. For somewhat acidic waters (lower than 6.5), forced draft degasifiers are the cheapest way to raise the pH, as the process raises the pH by stripping dissolved carbon dioxide (carbonic acid) from the water.

Lime is commonly used for pH adjustment for municipal water, as it is cheap. Acid (hydrochloric acid or sulfuric acid) may be added to alkaline waters in some circumstances to lower the pH.

So accordingly regardless of whether the water is from a limestone groundwater aquifer or an open water lake by the time it gets to us it is fairly well homogenised particularly if it was acidic in the first place since it is stripped of its CO2 by degasifiers.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Hi all,
I'm unconvinced about the "fluctuating CO2" hypothesis as well, have a look at this thread, as it may be from before you joined us <http://www.ukaps.org/forum/viewtopic.php?f=27&t=17798>.

I think you can explain the additional amount of CO2 in the tap water pretty well by "Henry's Law" and temperature.
At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid."
solubility-co2-water.png

From <http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html>

So assuming that the tap water is both colder than the tank water and under-pressure in the water main (which I think is going to be true all of the time) it will hold more CO2 in equilibrium, without the need for an additional source of CO2.

I also think that nearly all UK tap water comes out of the tap at well over pH7 as the water companies are very concerned with keeping inside the very tough EU limits for heavy metals, and are injecting NaOH (and adding orthophosphates PO4-) to ensure that no lead (Pb) or copper (Cu) ends up in solution. I assume they use NaOH, as it gives you most bang for your buck.

cheers Darrel
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

geaves said:
:thumbup: Now that I understand, having bookmarked your threads for continued future reference I find I get lost/confused by the 'applied science' on what is essentially growing immersed plants.

You can bookmark ALL of someones threads ? Including future posts ?
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Antipofish said:
geaves said:
:thumbup: Now that I understand, having bookmarked your threads for continued future reference I find I get lost/confused by the 'applied science' on what is essentially growing immersed plants.

You can bookmark ALL of someones threads ? Including future posts ?

You can bookmark any thread, once the thread is bookmarked you can go back and review it, re read it or keep for further reference. I've bookmarked some of Troi's threads, and threads where Darrel has posted re the duckweed index, for me due to the information that's on here bookmarking helps me build a sort of reference library on how I want to set up and run a planted tank. Plus if there's something that's not quite sunk in to start with I can go over it again, the bookmark option is at the bottom of each thread along with the subscribe option.

*Edit, also the bookmarked threads show in your control panel and will show any unread posts to that thread.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

bba on plant tips- one day later co2 runs out. (two months later) bba on plant tips, a day later co2 runs out....
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

dw1305 said:
are injecting NaOH (and adding orthophosphates PO4-) to ensure that no lead (Pb) or copper (Cu) ends up in solution. I assume they use NaOH, as it gives you most bang for your buck.

cheers Darrel

And these add hydroxide alkalinity (as opposed to carbonate alkalinity, making those pH/KH charts messy and well, not particularly useful). PO4 also can affect alkalinity.

Often times they do lime softening where they raise the pH to 10.1 or 10.2 to remove Calcium (Carbonate), then they add CO2 to drop the pH back down. Sometimes they blend with hard water in what's called partial lime softening and this drops the pH back down also, but the water is loaded inside a sealed system and cold, so all dissolved gas is much higher than our tank's temps.

Some folks seem to do okay with water changes on a non CO2 tank, I find them unneeded.
Many have tried water changes on anon CO2 enriched tank only getting algae over and over, fairly consistently.
This would suggest it is not CO2 independent of other factors.

But perhaps light intensity + CO2, or something else.

Also, the variation we are talking about is small, much smaller than the variation for the CO2 gas enrichment folks.
Things change in non CO2 systems much slower, but that's a good thing for most aspects.

A change from 0ppm to say 3-4ppm is a dramatic change for a non CO2 enriched tank.
A change from 40ppm to 45ppm is not for a CO2 enriched tank.

The type of plants also makes a large difference, some are weedy and will take up the light and start photosynthesizing at a much lower light intensity than other species. If the community of plants is fairly equal with light and CO2, then there's likely more even growth.

Willa one time change make a lot of difference? No, not much really, but consistent water changes might remove the ferts, but in the case with soil or ADA As etc......the plants still have nutrients.

Still, if you do not NEED to do the water change and are looking for a lower labor method, then it goes without saying and it works well.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Wouldn't a non CO2 tank that is fully stocked, or over stocked never reach equilibrium because the fish are constantly pumping CO2 into the water. Therefore a water change would result in a considerable drop in CO2. Tanks without many fish wouldn't have the same problem.

I know a guy that always had way too many fish, they were always dying, non CO2, big WC every other week and he constantly had tons of BBA all over his plastic plants and decor. Had to bleach it off all the time.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Hi all,
I've never added CO2, so I don't have any practical experience of the differences between non-CO2/CO2 added tanks.
I know a guy that always had way too many fish, they were always dying, non CO2, big WC every other week and he constantly had tons of BBA all over his plastic plants and decor. Had to bleach it off all the time.
I think that would be a pretty common finding. If you have a non-planted tank with low maintenance, a heavy fish load and enough light for plant growth, you end up with fantastic BBA growth. Our local pet shop, where they must kill more fish than they sell, has particularly gruesome BBA covered tanks, with the pea gravel looking like it has been coated with fake fur.
And these add hydroxide alkalinity (as opposed to carbonate alkalinity, making those pH/KH charts messy and well, not particularly useful). PO4 also can affect alkalinity.
This has been a major problem on some of the other forums I visit. A lot of people in the N and W of the UK, now have an alkaline supply with a high pH, but no carbonate buffering. With apologies for the cross-post, but have a look at this one <http://www.plecoplanet.com/forum/showthread.php?t=8904&page=2>.

There are some UK water treatment details here: <http://www.staffs.ac.uk/schools/sciences/consultancy/dladmin/zCIWEMPOTWAT/Activity5/act5.html>

cheers Darrel
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Overstocked tanks of any type have lots of issues, the algae is likely more helpful in that example :oops:

With CO2 enrichment, it's added for a few reasons: mostly to prevent CO2 competition and differences in uptake between plant species and within plant species. By adding non limiting CO2 for all plants, this competition is removed.

We can now grow any species easily together. This also falsifies the allelopathy claim as the plants all do exceptionally well no matter which combination or % is used. Individuals might have troubles with a species or two together....but if you ask the community of plant aquarist about the 2 species, someone has grown them well together on most forums, many ways to not have a plant do well, but if they do well together....then that claim is out the window.

Plants adapt well to low CO2. This is a large enzymatic cost however, the Rubisco concentration is greatly increased in leaf tissue vs the CO2 enriched tank. Same with low/limiting nutrient levels, but nowhere near the cost for CO2 acquisition.

If the concentrations vary environmentally a great deal, this "confuses" the plant and it tries to adapt and often stunts as a result if the changes are too great. This is not toxicity as some assume. It's stability.

Often times, the aquarist will simply dose less and it's not that less was better necessarily...........but rather they provided stability. If the CO2 dosing was poor..........and not corrected/assumed to be correct when it was not.......then limiting a nutrient would provide a stronger limitation than say CO2............then they see improvement and think that less is best and that adding non limiting nutrients causes algae, regardless of the evidence from other hobbyists.

However, adding more nutrients to NON CO2/Excel enriched system also does not cause algae if the CO2 is well adapted and stable systems are tested. A mucked up algae ridden system is not by the very definition a stable system.........but folks with such tanks think they can test and use kits to analyze their woes based on myths.

It's a bit of a problem in the hobby.

Still, a plant can handle limiting CO2 conditions well and some species are particularly good at it. The CO2 is highest at pre dawn and then drops near zero after a few hours of light. A wet/dry filter might provide more stable but lower CO2 for a non CO2 tank(say 1-2ppm vs say 3-5 ppm for pre dawn measures, but those drop after 2-3 hours tops to near zero).

Whereas the wet/dry will remain pretty close to the 1-2ppm range most of the day light cycle.
Seems that the 1st few hours(1-2) is the most critical time though. Same for CO2 enriched tanks also actually.
There is evolutionary support since this is the most competitive time for plants after a limiting resource, and for low light so they can start photosynthesizing before the other plants and nab all the limiting CO2.

Thanks for the post on the local water issues........always interesting and good to compare. I have been lucky here in the SF Bay area due to a wide range of tap waters being used and to compare growth.
This use to be a huge issue and question, debates raged on this topic, but these days, not so much.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

.........but folks with such tanks think they can test and use kits to analyze their woes based on myths.

It's a bit of a problem in the hobby.

I find this aspect of the hobby really intriguing, and the above quote kind of sums up in a nutshell what I was trying to highlight (rightly or wrongly) using the low energy/water change – unstable CO2/algae hypothesis.

I am fascinated by the complex and often unique synergistic biochemical interactions that are constantly at work in our tanks…

…but even more so by some of the spurious conclusions that even scientifically trained observers have drawn over the years to explain why, for instance, algae have mounted a surprise offensive whilst they weren’t looking.

And I include myself in that, but thankfully I kept some of my more outrageous theories on causality private and just as well because a far more sensible and simple theory is often just around the corner.
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Hi all,
the algae is likely more helpful in that example
Yes, I spend a lot of time on other forums explaining to people that "biofilm" is often helpful in the tank, and that "plants" (in the widest sense, including all photosynthetic organisms) are visible symptom that conditions are suitable for plant growth, and that the algae, duckweed etc is actually performing the useful task of turning nitrates into plant matter, but it often doesn't make any difference. Usually soon after this, they post back that since they got the UV light, or put an LED strip in rather than the fluorescent light, and their algae problems have ended. They then recommend this to every-one else. After that things usually either go silent, or they post that their fish are ill or dead, and the whole sorry scenario starts again with them then recommending nitrate reduction resins, a bigger, better filter etc to every-one who will listen, until the next episode of fish death.

I even get this from people with formerly planted tanks, who suffer night time fish death, correlate this with night time oxygen usage/CO2 production by the plants, and then get rid of their plants. Usually things are OK for a while until the dead fish are replaced, or the fish (and bioload), grow and the string of fish deaths etc begins again.

....By adding non limiting CO2 for all plants, this competition is removed. This also falsifies the allelopathy claim as the plants all do exceptionally well no matter which combination or % is used. Individuals might have troubles with a species or two together....but if you ask the community of plant aquarist about the 2 species, someone has grown them well together on most forums, many ways to not have a plant do well, but if they do well together....then that claim is out the window
I'm another allelopathy sceptic, there are 2 main reasons for this.
The first is why would plants develop allelopathy? when the majority of them have symbiotic relationships with micro-organisms (bacteria, actinomycetes, fungi etc,) that have been waging chemical warfare on each other since they evolved. Evolution isn't like that, it can't plan for the future, natural selection works on the genes that are already there. Richard Dawkins calls it "Climbing Mount Improbable", by which he means that an organism can't go back down hill in evolutionary terms ("become less fit"), even if there is a loftier peak they could then climb near by.

The second is less theoretical, and is just that if allelopathy was common in plants, you would find plants with no obvious competitive advantage in situations where they receive abundant nutrients, PAR etc. and it just doesn't happen. This isn't true of other situations and if you go to say a coral reef, a lot of the corals etc are waging very obvious chemical warfare with one another, and all sorts of small, slow growing, organisms are occupying prime sites.

Plants adapt well to low CO2. This is a large enzymatic cost however, the Rubisco concentration is greatly increased in leaf tissue vs the CO2 enriched tank. Same with low/limiting nutrient levels, but nowhere near the cost for CO2 acquisition.
I don't know enough about plant physiology to really pass any useful comment, but I can see that that abundant CO2 and nutrients will allow the plant to turn more of the PAR into Rubisco. I did find this paper from when I was a student, but I have no idea how general a finding this is, or what research has been done since.

Campbell, W. et al (1988) "Effects of CO2 Concentration on Rubisco Activity, Amount, and Photosynthesis in Soybean Leaves" Plant Physiol. 88 pp1310-13.
Soybean plants grown at elevated CO2 concentrations had heavier pod weights per plant, 44% heavier with 660 compared to 330 microliters of CO2 per liter grown plants, and also greater specific leaf weights. Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activity showed no response (mean activity of 96 micromoles of CO2 per square meter per second expressed on a leaflet area basis) to short-term (-1 hour) exposures to a range of CO2 concentrations (110-880 microliters per liter), nor was a response of activity (mean activity of 1.01 micromoles of CO2 per minute per milligram of protein) to growth CO2 concentration (160- 990 nucroliters per liter) observed. The amount of rubisco protein was cu as growth CO2 concentration was varied, and averaged 55% of tde $1 leaflet soluble protein. Although CO2 is required for activation of robisco, results indicated that within the range of CO2 concentrations used (110-990 microliters per liter), rubisco activity in soybean leaflets, in the light, was not regulated by CO2.
Whereas the wet/dry will remain pretty close to the 1-2ppm range most of the day light cycle.
I'm a lot more secure with this one, we weren't particularly interested in CO2, so I don't have any empirical measurements, but as oxygen is much less soluble than CO2, and this is true for oxygen.Because of I'm fairly confident that the large gas exchange surfaces of wet and dry trickle filters will deliver stable levels of all gases including CO2.

cheers Darrel
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

Hi all,
Just found that this Ph.D thesis - "ADAPTATION AND ACCLIMATION OF POPULATIONS OF LUDWIGIA REPENS TO GROWTH IN HIGH- AND LOWER-CO2 SPRINGS" is available from <http://ufdcimages.uflib.ufl.edu/UF/E0/00/09/94/00001/lytle_s.pdf>. So hopefully that should have some figures for L. repens at least.

cheers Darrel
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

dw1305 said:
I'm another allelopathy sceptic, there are 2 main reasons for this.
The first is why would plants develop allelopathy? when the majority of them have symbiotic relationships with micro-organisms (bacteria, actinomycetes, fungi etc,) that have been waging chemical warfare on each other since they evolved. Evolution isn't like that, it can't plan for the future, natural selection works on the genes that are already there. Richard Dawkins calls it "Climbing Mount Improbable", by which he means that an organism can't go back down hill in evolutionary terms ("become less fit"), even if there is a loftier peak they could then climb near by.
Dawkins is a science extremist, I got most of his books, he is ace but very one dimensional, the way he doesn't understand religion for example and his lack of philisophical insight, he is very reductionist. Anyway before I go off on one, genetic drift allows organisms to effectively move from one hill to another across the genetic landscape without having to "go downhill".
 
Re: Low Energy, Water Changes, CO2, Algae, and Pseudoscience

I find aquarium science interesting but I try not to actually apply it in this amount of detail to my tanks. What I mean by this is simply taking each tank on it's own terms and following a very broad set of guidelines which have been demonstrated to work. If something is working, it's working and no amount of theoretical assertions are going to change that, but if something starts to go wrong then I'll break out the science and start looking into what's happening.

Reading thread's like this I get the feeling that many of us are overcomplicating what is in essence, a fairly simple hobby. Plants need light, co2 and nutrients. We can spot co2 and nutrient deficiencies and we can estimate approximate lighting levels. It doesn't really need to be more complicated than that.
 
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