Results 1 to 10 of 49

Thread: Methods: algae control or growing plants?

Hybrid View

  1. #1

    Methods: algae control or growing plants?

    Many dosing methods suggest that they have some way of solving all your algae issues. Curiously, such methods also fail to address algae growth and causes at the root.

    While a method might work to solve the issue of a noxious algal bloom in your aquarium with plants, why it does it, is a matter of debate. Therein lies the crux of myths in the hobby and why I am writing this.

    PMDD:
    Control of Algae in Planted Aquaria

    This is a method to address algae in the aquarium.
    However, it is really a method to grow aquatic plants.
    Aquatic plants require 3 main things to grow: light(they suggest enough, however on the low side), CO2, (also on the low side, but error in measurement and low light play a large role there as well as dependency on limiting PO4, which reduces CO2 demand, indirectly stabilizing CO2 availability to plants) and nutrients.

    Since nutrients are LIMITING with PMDD, PO4 specifically, the effects on CO2 are also present. CO2 at 10-15ppm at low light and under strong PO4 limitation will work.

    However, adding PO4 will induce a number of algal species in this system.

    To test whether it is really PO4 limitation that is causing algae to be controlled, we must ensure that CO2 is also not limiting and scaled up when the PO4 concentration is increased.

    Many aquarists see that adding PO4 or allowing it to become higher= algae blooms for their systems, yet cannot explain why other aquarist can have high PO4 without any trace of algae for years, even at low, medium and very high light intensities.

    This reduced CO2 dependency due to strong limitations of nutrients (PO4 is one of the better nutrients to chose), is based on Liebig's Law of the minimum.
    If PO4 is strongly limiting, adding more CO2 will do nothing to enhance the rates of growth. You can add all the CO2 in the world and the plants will not grow more, the PO4 is the bottle neck, not CO2.

    Still, the aquarist who finds management of PO4 = less algae will remain unconvinced, yet have a conflict with other aquarist that have high PO4 and no algae. However, simply because they chose or cannot maintain good higher CO2 along with higher PO4, does not imply they are correct.

    Some people simply do whatever works for them and are resistant to change or learning a new method that addresses balances of light, CO2 and nutrients and scaling up or down depending on light intensity etc.

    There is nothing wrong with that.
    However, to suggest to other hobbyists that it is the cure and the root cause for controlling algae is......well.............very poor logic and even poorer experimental test protocol.

    I suggest hobbyists keep good plant growth and algae in 2 separate groups.
    PMDD address plant growth perhaps more than algae control.
    PPS does something very similar to PMDD, as does Redfield ratio, MCI, and few other methods aimed at controlling algae through nutrients, mostly all of them have one central component: limit PO4.

    What does PO4 limitation do?
    Is it really limiting algae?
    No, not really.

    That metric is extremely low, beyond the limits of test kits and methods used in the hobby. Less than 10 parts per Billion.

    So what is occurring?
    Well, using Liebig's law, we see that PO4 is more strongly limiting than CO2.
    Thus the plants are better able to handle and withstand PO4 limitation, than CO2 limitation. This is a plant issue, not an algae issue.

    We can go back and instead of limiting plants and forcing them to reduce their CO2 demands via PO4 limitation, we can add CO2 at a higher rate and also add more PO4 at a much higher rate. So CO2 and P4 are both non limiting.

    If you only test one side of the coin, you leave yourself open to false conclusions, even if they might work to cure the algae, they do not explain why the algae is gone nor are able to explain why other observations show that high PO4 also does not induce algae.

    So what does induce algae growth?
    This is a different question that how to get rid of algae.
    Very different and specific.

    The answer/s is/are not as nice. They are specific to each and every species of algae. They involve space and time (Ecology), light, CO2........and nutrients.........as well as the status of the plants.

    How might we test for algae inducement independent of good plant health?
    1. You must have a reference control. This means a nice well run tank with plants, no algae and non limiting CO2 AND NUTRIENTS. Light can be easily manipulated for PAR and is the growth rate determination when CO2/nutrients are non limiting(up to a point where metabolic growth rates can longer be increased, the maximal yield).

    2. Test light, go from the lowest possible to highest possible PAR. Vary and adjust the duration. Can light manipulation control algae the same way that PO4 limitation can? Certainly and better even. By reducing light intensity, this also reduces CO2 demand(there will be difference depending on how strong of a reduction light or PO4 might be for each case). Still, most aquarist have long noted reducing light intensity "cures algae". Why this is still is based around "Light= drives CO2 demand= drives nutrient demand".

    If you limit nutrients strongly, then adding all the CO2 and light will not change the rates of growth, likewise, if you limit light, then attaining ample CO2 and nutrient is much easier as well, algae also grow slower, since their only limitation is really light intensity.

    3. Test CO2. This is more difficult. CO2 measure is the hardest parameter to come to grips with. By adding good ample known PAR intensity for a plant, and non limiting nutrients, now we can test CO2 effectively. We may also add sediment types to this, both plain sand and enriched soils, to see if sediments play a role or not and to add as a back up for nutrient limitations/preferences within the root zones as well as the water column.

    Since light and nutrients are independent, CO2 is the only dependent variable.
    By adjusting CO2, we can induce and cause germination of dozens of species of algae.

    Only when there is dependence on other variables with PO4 limitation control methods, do we see algae issues(Say adding PO4 to 2-3 ppm).

    This suggest it is CO2, not PO4 that is controlling germination for many algae species. Perhaps.........but it might be due to plants and Carbon uptake that signals algae to start to bloom, not CO2 directly either.

    Still, we know PO4 alone cannot account for algae blooms for all systems and we know we can consistently incduce algae independent of nutrient and light with CO2. We cannot consistently induce algae with varying just the PO4 when other nutrients and CO2, light are independent.

    The only conclusion is that limiting PO4 is not limit algae, rather some other cause must be present. This does NOT............discount that in some planted systems, that limiting PO4 does show a reduction in algae. but that the cause is indirect and related to CO2, not PO4. to test this, we simply add more CO2 and raise the PO4 and we no longer have algae blooms.

    This still does not imply cause that CO2 is the key.
    It is only 1 step closer at getting at the root cause.
    From a management perspective for control of algae, CO2 is central.
    The same is true in a non CO2 aquarium, CO2 stability is key.

    Plants have a rough time adapting to different CO2 levels, algae do not(they are virtually never limited by CO2). Plants need to make a lot more Rubsico to adjust to lower levels, often several times more(10-20X with CO2 enriched vs no CO2) and it takes time for the plant to make these enzymes.

    Changing CO2 around day to day, hour to hour, week to week the plant struggles and spends more energy adapting to CO2, than with growth, acquiring nutrients, catching light etc. In non CO2 systems, changing water frequently causes a spike in high CO2 week to week etc, done only once every few months is better.

    For CO2 enriched tanks(non limiting CO2 systems), changing water has no such impact. The plants do not need to adapt to CO2 since they have ample CO2 and supply for all conditions.

    We may also limit CO2 slightly and PO4 and have somewhat stable systems also, but these are harder to duplicate. Still, plants will adapt moderate levels of CO2 as long as they are stable enough for maintaining the same Rubsico concentration in the tissues.

    So often,m not doing water changes (or as much) in these reduced CO2 systems(like PMDD suggested 10-15ppm) will work well and appear to reduce algae. Still, these systems are still limited by CO2, the plants have adapted, just like the non CO2 systems. As long as the CO2 is stable and does not change/vary much week to week, the plants should still grow well and reduced, but algae free.





    Both of the above curves show that at lower levels, the yields are reduced in the limiting ranges. It is not black and white, they have varying degrees of limitation.
    Mild limitation has less effect on overall growth, while large effects on CO2.
    Very strong limitation has a pronounced effect on growth and deficiencies.

    The adequate and C/B zones give the aquarist the most leeway for dosing, both CO2 and nutrients, as well as light.

    It is only when the CO2(or nutrients, or light) are in the D zones that we can be sure that they are independent when we test the other parameters.

    Regards,
    Tom Barr

  2. #2
    Back to algae.

    Perhaps nutrients can play a role?
    I used NH4 and found under high dosing(1-2ppm) and high light, I managed to induce Green water. CO2 reduction also increased the rates of growth for green water(less CO2). GW is common in new aquariums with high light(uncycled tanks, without bacteria and good plant growth, no NH4=> NO3 cycling going on).

    NH4 is the only nutrient I have found to induce GW, also, progressively increasing bioloading to a breaking point where algae bloom also produced a similar effect.
    This suggest that NH4 plays some role. However, others have dosed NH4, as I have as well, and not been able to induce GW or other species. So such results are likely inconclusive. Perhaps poor CO2 played a role and light intensity? Perhaps peat, tannins, sediment types play a role? Some have suggest it also.

    CO2(varying it below non limiting levels) and high light are very consistently however. They can induce many species of algae. Low PO4 also appears to induce GSA. Low CO2: BBA, and staghorn(with high bioloading), BGA appears to be low NO3, but also organic matter.

    Each algae has it's own set of parameters it correlates with. there may also be more than 1 single cause for algae blooms as well. Still testing what will induce algae in an other wise independent system by manipulating one parameter at a time is the best way to see why algae grows and how to stop it. MCI suggest strongly limiting PO4 for a few weeks till you get GSA...then raising it back up and after the other algae has gone away, this will get rid of GSA later. In GW blooms, few other algae species will grow also, so you can use algae and PO4 limitations etc or inducement to control harder to eradicate species also.

    Still, we can do the same eradication with light reduction, or with good CO2 stability. Generally, aquarist find a lot more utility and success watching light and CO2 and of course, the plants. Nutrients are rather easy to dose/add etc. Plants will adapt to lower, higher levels, just like CO2, as long as the inputs are stable.

    Where many go very wrong in their conclusions, is that more nutrients induce algae. This is simply not true. This only occurs when there is dependency on other parameters like CO2.

    While this might ruffle the feathers of the folks who promote such PO4 limiting methods..........to be told that it cannot be due to limitations directly challenges the claims made, it is what it is, those are the results and cannot be reconciled is terms of the hypothesis : limiting PO4 is what controls algae.

    That is testable and has been falsified. The hypothesis cannot explain how high PO4 does not induce algae. If the hypoithesis is high PO4 = algae, then it should be tested.
    It can be reworded, repackaged any number of ways, but without addressing the light, the CO2 and nutrients independently, the method will still lead many to a wrong conclusion.
    This does not imply limiting PO4 is not a viable option for algae control.
    It is and has been for decades, but why it works has been falsified in terms of limitation of algae.

    Getting at the root causes for germination of algae is a more productive method at control options.
    Now we have more tools available to approach control of algae, not just limiting PO4.
    Increased CO2, reduced light intensity, better current, better filter cleaning, keeping biomass the same etc, adding liquid carbon supplements in conjunction, water changes(or reduction of them), reconciling why various methods work in a holistic approach to plant growth including non CO2 methods. This also allows us to test better and look for more causes rather than putting all of our "eggs in the *nutrient* basket". That is risky.

    In terms of management, we need a hypothesis that addresses several methods, several seemingly contradictory observations, and that explains why it works for each method chosen by the aquarist.
    This gives us the best explanation, the most tools and makes the most sense. It also helps us to focus on plant growth, then when algae does come along, we know what each species is a bioindicator, or a "test kit" of.
    This makes management easier as well for algae and plant growth.

    Regards,
    Tom Barr

  3. #3
    http://fishweb.ifas.ufl.edu/Faculty%...macrophyte.pdf

    Suggest no relationships between natural lakes and aquatic plants and nutrients, thus it appears to be some other mechanism besides just limiting PO4(eg CO2 and light, actual starting state of the lake).

    Regarding ratios and the RR(Redfield ratio):
    This statement is from Anderson's "Algal culturing methods" text(2005):

    The RR "is arguably one of the most abused parameters in the field of aquatic ecology. the RR is an approximation of of a composition averaged over very large scales of time and space and does not describe the conditions of individual cells and populations".

    Anderson goes on the cite several chemostat studies where the ratio for the freshwater Scenedesmus was 30 N:1 P, nearly 2 fold difference, 25 to 33 for a diatom, Pavlova , 35-40 for the diatom Chaetoceros. It is expected and does vary with irradiance(light.

    So light, the species in question, all make a huge difference in these limitations and ratios, particularly when they ARE APPLIED TO ALGAE. Even so, using RR and increasing the concentrations 5-10 fold on both sides of the ratio will ensure the algae is not limited by either nutrient.

    Anderson suggest that unless carbon limitation is a goal, air bubbling will suffice for Carbon supply.

    Many studies support the CO2 compensation points for algae are in the 0.1ppm ranges for the higher green freshwater algae species. Here is a review of 16 freshwater species:

    Measurement of Carbon Dioxide Compensation Points of Freshwater Algae -- Birmingham and Colman 64 (5): 892 -- PLANT PHYSIOLOGY
    Photosynthesis and Photorespiration in Algae -- Lloyd et al. 59 (5): 936 -- PLANT PHYSIOLOGY
    Measurement of Photorespiration in Algae -- Birmingham et al. 69 (1): 259 -- PLANT PHYSIOLOGY

    22 ppm of CO2 is = about 0.5milliMoles of CO2.
    The above ranges for algae are less 2ppm for all.
    Most are less than 1ppm, amd some are down in the 0.1ppm ranges.


    Compared to plants which saturate at 20-30ppm for aggressive aquatic weeds with excellent aggressive CO2 and Bicarbonate uptake mechanism (this is why they are so competitive and aggressive):

    http://www.plantphysiol.org/cgi/reprint/58/6/761.pdf

    .5 to .6 mM of CO2 was the maximum CO2 range at high light for these easy to grow weeds. More CO2 was required at lower pH since these plants can and do use Bicarbonate as a source of carbon.

    If you look at figure 6, you can see how much more aggressive Hydrilla and coon tail are compared to Cabomba and Milfoil. These species have different abilities to utilize light and CO2.

    Aquairst assume thast all aquatic plants are equal when it comes to adding enough CO2. Clearly there are demonstrated differences in the research and within the aggressive noxious weeds which are better at acquiring CO2 than say HC or other aquatic plants, of which there are 300-400 species. surly they cannot all be aggressive noxious weeds with the same abilities to take up CO2 from solutions of use bicarbonates as a source of DIC.

    Algae are wide in their ranges and nutrient, CO2 and light demands as well.
    The points here are that we should very careful when generalizing what is a limitation, how important a ratio is/is not, and what other affects such as KH(higher pH's in the above study using NaCO3) and the ability to use HCO3.

    It is no secret why I have had few issues growing every species of aquatic plant to a high level and resolved algae issues effectively.

    I ensure there's ample CO2 for plants, above and beyond the minimums set in such papers referenced above, perhaps 30ppm of CO2 is too low even for some species, while plenty of other species. Hard to say without doing the research on those specific species in question. With 300 or more species to test, that's a lot of research yet to be done. Rather than that approach, adding excess levels that ensure all species have ample CO2 seems a better management approach.
    While we may be curious as to the CO2 compensation points of the various plants, we in general, just want to know how much to add to ensure we are not CO2 limited.

    The other issue is getting at the root cause for the algae germination bloom.
    We can kill algae many different ways and remove it, nutrients, CO2, limiting light etc, chemical treatments etc..........but prevention is wiser than a pound of cure.

    That is the key and it is focused on the plant's growth and health.
    Plants, not nutrients define and maintain the system when they are in ample supply.

    Same is true in many other fields wit pest, farms etc, weeds do not get established and become an issue unless poor management is done and poor crop health occurs.

    Algae are also sexual and have many asexual stages in aquatic systems that our plants simply do not have available, this allows the algae to survive brutal environments and high and low nutrients, light, and CO2 levels. Understanding what those signals that cause algae to go into these stages is key to stopping their continuing growth. Adult algae tend to be short lived, so if you stop new growth and stop these cycles, you stop algae.

    As long as you can grow aquatic plants still while treating algae, then the method should work well(nutrients, CO2 or light or a combo of the 3, or chemicals etc).

    Regards,
    Tom Barr

  4. #4
    Join Date
    Oct 2007
    Location
    Brisbane, Australia
    Posts
    824
    Thanks for putting that together Tom, it is a good read and very helpful.

  5. #5
    Join Date
    Jul 2009
    Location
    The Netherlands
    Posts
    2,280
    Very good article en very helpful. Thanks.
    Last edited by dutchy; 08-27-2009 at 09:59 AM.
    regards,
    dutchy.

    My 2011, 2012 and 2013 AGA aquascaping contest entries:
    http://www.barrreport.com/album.php?u=21013

  6. #6
    thanks for sharing, this is a very insightful read

  7. #7
    Quote Originally Posted by Tom Barr View Post

    Many studies support the CO2 compensation points for algae are in the 0.1ppm ranges for the higher green freshwater algae species. Here is a review of 16 freshwater species:

    Measurement of Carbon Dioxide Compensation Points of Freshwater Algae -- Birmingham and Colman 64 (5): 892 -- PLANT PHYSIOLOGY
    Hi Tom,

    correct me if I am wrong.
    1 microliter ( μL ) per liter = 1 ppm, reference: http://www.engineeringtoolbox.com/ppm-d_1039.html
    right?

    So, the CO2 compensation points of 16 freshwater algae ranged from 4.8-41.5 microliters per liter (or 4.8-41.5 ppm) at acid pH,
    while at alkaline pH they ranged from 0.2 to 7.2 microliters per liter (or 0.2-7.2 ppm).

    Obviously algae adapted easily to the alkaline environment. But in the acid environment, I am not sure if algae are doing any better than the aquatic plants? How do we rule out that it is CO2 ALONG that control the algae bloom but not the accompanied acid environment?

    Regards,
    Erich


  8. #8
    Quote Originally Posted by paludarium View Post
    Hi Tom,

    correct me if I am wrong.
    1 microliter ( μL ) per liter = 1 ppm, reference: http://www.engineeringtoolbox.com/ppm-d_1039.html
    right?

    So, the CO2 compensation points of 16 freshwater algae ranged from 4.8-41.5 microliters per liter (or 4.8-41.5 ppm) at acid pH,
    while at alkaline pH they ranged from 0.2 to 7.2 microliters per liter (or 0.2-7.2 ppm).

    Obviously algae adapted easily to the alkaline environment. But in the acid environment, I am not sure if algae are doing any better than the aquatic plants? How do we rule out that it is CO2 ALONG that control the algae bloom but not the accompanied acid environment?

    Regards,
    Erich

    you simply use an acid/base system that does not use CO2/HCO3, then see what effects the pH has...........in the acid ranges.......peat,. tannins often do this in natural systems, so that would be one idea.........then other acids and base pairs can be used also.

    Then the CO2 can be controlled independently and then deterime if there is much effect on growth, algae, plants etc.......

  9. #9
    Quote Originally Posted by Tom Barr View Post
    you simply use an acid/base system that does not use CO2/HCO3, then see what effects the pH has...........in the acid ranges.......peat,. tannins often do this in natural systems, so that would be one idea.........then other acids and base pairs can be used also.

    Then the CO2 can be controlled independently and then deterime if there is much effect on growth, algae, plants etc.......
    Thanks Tom.

    Aside from algae, according to this study on three aquatic weeds, http://www.plantphysiol.org/content/58/6/761.full.pdf, Hydrilla and Ceratophyllum had CO2 compensation points of 44 and 41 microliters per liter, respectively, whereas the value for Myriophyllum was 19. Most of the algae lay in the range of 15 to 20 microliters per liter. http://www.plantphysiol.org/content/64/5/892.short.

    In terms of CO2 compensation points, is Myriophyllum spicatum a more competitive species, but not Hydrilla or Ceratophyllum?

    Regards,
    Erich

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •