Discussion in 'User-Created Articles' started by jhnrb, Sep 29, 2005.

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  1. jhnrb


    Mar 9, 2005
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    PART 1 - Red Slime Algae and Cyanobacteria in general

    -An Introduction

    Blue green algae, or Cyanobacteria, are remarkable in as much as they are somewhat of a hybrid between algae and bacteria. In some ways they resemble green plants and algae, and in others they are much closer to bacteria. The latter explains why antibiotics are sometimes used to rid the tank blue-greens.

    Although this method results in their disappearance, at least for a while, the dangers associated with using them in an aquarium need to be stressed here.

    Biological filters contain many bacteria themselves. These, too, can be affected and more than likely will be. This can lead to ammonia spikes in the tank due to the loss of the bacterial bed (partially or completely). Note that since live rock and live sand contains bacteria as well, the use of antibiotics will affect them as well.

    Cyanobacteria are photosynthetic. They release oxygen and uptake carbon dioxide, depending on the photoperiod and lighting conditions. Cyanobacteria contain pigments. The prevalence of one particular pigment ultimately determines the color of the algae.

    It should be noted that they are among the oldest form of organisms found on earth. Traces of cyanobacteria have been found in fossils dating from the early Precambrian period, some 3 billion years ago. They are extremely common, even today, and are found in fresh, brackish and salt water. They are present even on land in moist environments. Cyanobacteria, referred to as blue-green algae, come in various colors.

    Do not let the name confuse you. They are not necessarily blue-green but can be blackish, greenish, blue greenish, yellowish, brownish and reddish. The latter color is perhaps the one most saltwater hobbyists are familiar with.

    Note that your aquarium doubtlessly contains many more cyanobacteria than you are aware of. The main reason being that many of the various forms of cyanobacteria are present in any environment where photosynthesis takes place. Their numbers may be small and their size certainly is. You do, therefore, not notice them.

    At times though they become really conspicuous because they agglomerate and form masses and patches. By themselves they are extremely small and are generally studied under an electron microscope, lest they would not be visible.

    The appearance of blue-green algae is always a disappointment to the hobbyist. Regardless of the type though their presence indicates a disturbance of the biological equilibrium in the tank.

    Blue greens are neither algae nor bacteria. They exhibit characteristics of both and can thus be considered an evolutionary link between the two. From the standpoint of cell structure they are clearly bacteria. From the perspective of their photosynthetic ability and the presence of pigments, they are algae.

    Note that not all cynobacteria occur in saltwater and that some are free floating and non benthic. The free floating ones are removed by skimming mostly. The benthic ones are the ones that attach to rock, glass, acrylic, sand and anything else in the aquarium, including other types of algae.

    The simplest forms of cyanobacteria are the unicellular ones (Chroococcales). They reproduce by binary fission (splitting in two, then again in two, and this process is repeated over and over. Some split and do not remain together and become free floating. Others, as in Microcystis agglomerate and make up a large colony held together by a slimy mass. What you see, in essence, is not an alga but literally thousands upon thousands of them, all bound by the slime - the latter being what you see, not the individual algae. Remember they are so small that even normal strong microscopes cannot detect them.

    Many blue-greens are characterized a filamentous appearance. This results from binary splitting where the split cells string themselves together, one attaching itself to the other and so on, until what appears like a filament is present (e.g. the types that may grow on your glass and seem not to go away even when phosphate levels are real low. The reason for this will become clear later. Indeed their main food source is not PO4 but nitrogen, which they uptake directly from the water.

    Filaments can be straight as in Oscillatoria, or appear like a coil as in Spirulina. Of course variations occur that result from the shape of the actual cell (round, plate-lie, cylindrical, ovoid, rod-like, etc.). All these affect what you see. Again a slimy mass may hold the cells together, giving the algae the appearance of strings of slime rather than patches of slime. The strings can be straight or curled or even branched. Often the visible eye cannot detect the exact shape of the filaments even though they are made up of thousands and thousands of individual cells. There are so many cells though, that we see a filament or a patch or something similar.

    The shape of what you see can also be affected by whether or not the cells are all identical in shape or not. Indeed some of these algae cells' shape will change depending on what type of nutrients are available at the time the splitting occurs. Nitrogen availability levels and types appear to be the determining factor in the shape and size the cell takes on when division occurs. By type of nitrogen source is meant: nitrogen, nitrogenous compounds, nitrogen nitrate, and so on. Genetics appears to determine the positioning of the cells but not necessarily their size. The postulate is that the food source at the time of splitting has lot to do with size.

    The peripheral (outer) region of the cell contain the photosynthetic algal mechanism and the ensuing pigments.

    Depending on what pigments are present in that region and in what Carr calls supramolecular complexes, various color forms appear. It should be obvious that the type of lighting used may influence the growth of these algae. Indeed pigments absorb certain wavelengths of light. The one that we are probably most concerned with, the red slime algae, have a great deal (relatively speaking) of phycoerythrins. The latter's absorption level is optimized at 555-564 nm wavelength.

    Aquariums where a high amount of this light wavelength is present are, therefore, much more likely to see the appearance of red slimy algae, given that nutrients will be present (any nitrogen based food source - or in other words breakdown from protein or stated differently yet, dissolved organic matter or dissolved organic carbon).

    Red phycoerythrin is not the only pigment that is present in these algae of course and is what differentiates (amongst other characteristics) the blue greens. Blue phycocyanin and allophycocyanin are present in some as well. These have different wavelength uptake patterns and result in some blue greens taking on other colors. In addition, some blue greens have a mix of these pigments and the eventual color they take on depends on the spectrum of the light over them aquarium, as this will favor one pigment over another, meaning one color versus another one.

    For the sake of completeness the pigments just mentioned are Phycobiliproteins. This is in contrast to other pigments such as Chlorophyll and Carotenoids. All pigments in blue greens are incorporated in the lipid outer layer, referred to earlier (lipid=fat and fat-like esters). After being harvested by phycobiliproteins in the PS II (photosythesis II) cycle, light wavelength energy now trapped is transmitted to the PS I system and its Chlorophyll (mostly of type a). Clearly light is a major player in the type of blue-green algae that will appear.

    When we talk about light in the context of photosynthesis we always need to take into account that what we are really talking about is two distinct aspects of light: its intensity and its spectrum. Intensity can be viewed as its amount, spectrum can be seen as its quality. Both play a role in how much and what type of blue-green algae (and for that manner any photosynthesizing algae) will appear.

    It is also known that other nutrients play a role in the growth of blue-greens: iron, phosphorurs, magnesium and so on. Although the main nutrient appears to be nitrogen in many forms, this is not the only nutrient source these algae rely on and which makes them appear in an aquarium or aquatic environment.

    (cont. to part 2)
    Last edited: Sep 29, 2005
    jhnrb, Sep 29, 2005
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  2. jhnrb


    Mar 9, 2005
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    Part 2 Cyanobacteria & Red Slime Algae

    Cyanobacteria and Blue-Green Algae Part 2

    -In Part 1 we touched on the reproduction of Cyanobacteria: binary fission, budding, fragmentation. These forms of reproduction explain to a great extent the various appearances that Cyanobacteria take on in the aquarium: patches, slimy masses, strings, filaments, branched filaments and so on.

    We have seen that photosynthesis plays a large and important role in the reproduction and growth of such algae. The wavelength of the lighting that you provide determines what form of Cyanobacteria will grow in the tank. Keep the wavelengths that particularly promote blue-green algae growth low and you will have far less problems.

    We have also noted that other nutrients play a role in growth and reproduction (dissolved organic carbon or material being an important one). Phosphate and iron are other ones.

    Because of the usually high amount of pigments present in Cyanobacteria (as mentioned in Part 1), and because these pigments assist in the photosynthesis process light does play a great role in their growth and bears looking at some more. Indeed, slime algae of various colors can appear when the light source has degraded and when the wavelengths mentioned in Part 1 are suddenly becoming stronger (more intense or appear as a greater proportion of the total amount of lighting provided that penetrates the water.

    This is often overlooked. Hobbyists are more likely to look for other reasons to explain the blue-green growths, and forget that old bulbs, fluorescents tubes, and other forms of lighting may need to be replaced to eliminate the spectra that are undesirable in terms of their effect on Cyanobacterial growth in general.

    Photosynthesis can best and in its easiest form be described as the synthesis of organic compounds through the uptake of carbon dioxide and its fixation, light being used as the energy source.

    What is important to note is two-fold at least:

    -carbon dioxide is required, and it can come from two sources decay of organic material and bicarbonates in the water.
    -energy from light is required. This light has to be of the right spectrum (Kelvin degrees), as outlined in Part 1 of this article on blue-green algae.
    The carbon dioxide can come from the breakdown of organic material but can also come from bicarbonate ions. A high dissolved organic load, combined with a high dKH, is practically certain to lead to the appearance of blue-greens. Higher or greater amounts of photosynthesis, with at the same time the presence of a great deal of organic material in the water, will produce more CO2 on one hand and increase growth on the other. Higher amounts of light combined with more CO2 provide more energy and since the carbon dioxide is present, blue-greens will start to grow.

    The ideal combination for blue-greens to grow is: high DOC (dissolved organic carbon = dissolved organic protein = dissolved organic matter and the decay of that organic matter), high dKH levels and over saturation of CO2. The latter can occur if and when the carbon dioxide is not degassed properly from the water through the overflow leading to the sump, or when the water enters the sump by falling down in it in small streams.

    If no sump is present at all the likelihood of carbon dioxide being high increases. Add to that lighting ot the type of wavelengths indicated in Part 1 and you are just about sure to get blue-green algae to grow in your aquarium. Add a high dKH and you really have an ideal environment for Blue-Greens to appear and proliferate and be hard to eradicate.

    Bicarbonates (such as baking soda - another reason not to use it often or on a large scale to maintain pH levels which it does not really do anyway since its natural pH is between 7.6 and 7.8) is converted to carbon dioxide by means of an enzymatic process:

    HCO3- +H+ turns into CO2 + H2O.

    CO2 does not require light necessarily. That is why such carbon dioxide fixation is referred to as the "dark reaction" of photosynthesis. Carbon dioxide can be uptaken even when no light is present. When other conditons are not favorable to the growth of Blue-Greens, they will not appear in your tank. If they are though, they will. Other conditions, and in the one that contributes most to the growth of blue-greens is the presence of high amounts of dissolved organic material which really creates an ample supply of carbon dioxide and the presence of phosphates.

    Since photosynthesis is at work, photolysis occurs (also called the Hill Reaction) and oxygen is produced as a by-product. This is normally only associated with macro green algae but it should be clear from what has been written here that this oxygen production and release occurs with blue green algae as well. The actual reaction breaks water up into 2 Hydrogen ions, half an oxygen one and 2 units of energy. This explains why blue-greens soon are covered with tiny bubbles. The bubbles are free oxygen.

    While this free oxygen greatly contributes to dissolved oxygen levels in the tank, the fact that it is generated by algae we do not really want in our aquarium, makes it a process we do not wish to rely on.

    In nature though, blue-green algae are a very important source of oxygenation and play a very positive role in maintaining water quality at high purity since free oxygen has a real high ORP and cleans the water a great deal. In aquariums though we wish to achieve oxygen saturation in other ways, not through blue-green algae.

    The kind of lighting that is provided affects the growth cycle and determines the type of Cyanobacteria that actually make their appearance is a major factor to consider. What differentiates Cyanobacteria from other algae that photosynthesize, and especially from Chlorophyta (the higher green algae) is the wavelengths at which photosynthesis can take place.

    Chlorophyll plays a role and that the ideal wavelength for this process is the 665-680 nanometers wavelength. Specific to Cyanobacteria and what makes them different and may lead to their appearance is when the light emitted by whatever bulb you use, start to shift and emits wavelengths in the 620 and 560 nanometer range where the phycobiliproteins referred to in Part 1 are just as efficient at photosynthesing than chlorophyll is.

    This is a major difference specific to Blue-Greens.

    At those wavelengths phycocyanin and phycoerythrin photosynthesize and lead to the appearance of Cyanobacteria. A slight shift in the amount of light emitted in this waveband can therefore lead to an outbreak of Blue-Greens. Unsuspecting Hobbyists may try to find all kinds of reasons for this growth when all that is really happening is that their bulbs need changing as they are emitting light that is promoting the growth of Blue-Greens.

    Chlorophyll is still involved in the process but what is happening is that the pigments that can uptake the shorter wavelengths transfer it to the ones that need higher ones and so on. A typical sequence of the full photosynthesis cycle of Cyanobacteria would then be:

    » energy uptake and transfer from phycoerythrin to phycocyanin, to allophycocyanin, to chlorophyll a. The rest is quite clear. As photosynthesis proceeds and all the processes start to take place, Blue-Green algae suddenly appear in the aquarium.

    The picture is more complex still in certain cases and that other pigments and other nutrients are involved as well in the growth. Perhaps this explains why when these algae appear it is so difficult to deal with them and also explains why they appear when we as Hobbyists believe our water quality parameters are such that none should grow.

    Remember though: the main culprits are dissolved organic material and carbon dioxide and light of the wavelengths indicated above.

    (cont to part 3)
    Last edited: Sep 29, 2005
    jhnrb, Sep 29, 2005
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  3. jhnrb


    Mar 9, 2005
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    Cyanobacteria Part 3

    It has always been assumed that blue-green algae relied for the most part, if not completely, on photosynthesis for growth and reproduction. This may have been the case up to a few years ago but recent findings have demonstrated that Cyanobacteria do not rely solely on CO2 fixation but can and will thrive in environments that are rich in organic matter. To eradicate blue-greens one needs to skim more efficiently and/or use a compound that oxidizes organic material out of the water so this food source is no longer present.

    Most saltwater cyanos rely on either organic foodstuff uptake and/or on photosynthesis (and are called Facultatively Photoheterotrophs), and will uptake organic food and substances if they are available.

    Of course, we all know that our aquariums are laden with organic material. This is especially so if the skimmer we are using is not removing organic material efficiently or cannot remove all or the majority of it because it is either too small, or the tank is so heavily stocked that the skimmer cannot keep up with the amount of organic material produced on a continuous basis. Overfeeding would obviously contribute to this situation even more.

    It should be noted also that "light" actually enhances the uptake of organic material. The situation this puts hobbyists in is that not only are we faced with blue-greens that feed on organic substance and their breakdown components, but that light increases the uptake of these substances and results in a more dense and more widespread growth of cyanobacteria. Sort of a Catch 22 situation, unless we realize that we need to do what ever is in our power to keep the amount of organics in the water low, as low as possible. This requires the use of real efficient skimming (hobbyists who do so, do not generally report problems with outbreaks of Cyanos.

    What we definitely need to remember from this is that the combination of running high intensity lighting and not paying attention to the amount of organic material in the tank will definitely lead to the appearance of blue-green algae, as should be evident from the information given above. Two methods may to be used:

    -Skim as efficiently as you can.
    -Remove organic material from the aquarium by using an oxidizer (for instance potassium permanganate solutions such as Redox +).
    Excellent skimmers abound nowadays. As a rule of thumb it is a good idea to buy one that is rated for at least twice the size of your tank and to acquire a venturi type. Remember that for venturi skimmers to run well they need to be operated with pumps that can develop a lot of pressure on the venturi valve (this allows it to pull in more air and produce smaller bubbles which results in more efficient skimming). In addition to running such a skimmer, you may wish to add potassium permanaganate in small amounts a few times a week.

    One way to determine whether your organic load is high is to perform a DO and a BOD test (dissolved oxygen and biological oxygen demand). This is done in the following manner:

    -Take two samples of water.
    -Use one for immediate testing
    -Store the other in the dark making sure there is no air trapped in the
    container you use (fill it under water and then put the cap on).
    -Test the first sample for dissolved oxygen and write the result down
    -Store the second sample for 48 hours
    -After that time has elapsed, perform a dissolved oxygen test on the second
    -Write down the result
    -Compare the results of the first test to the second one and note what the
    difference is
    If it is greater than 1 mg/l your organic load is high and you definitely need to intervene. This is done either by upgrading the skimmer or making it more efficient, or starting a potassium permanganate solution treatment. Ideally and in most cases the better method is to do both.
    Note that even though the tests reveal to some extent what the DOC (dissolved organic carbon) level is, any protein material that is in the tank that has not decomposed yet is not measured by this test and will eventually increase the amount of DOC even further.
    It is important for correct DO and BOD measuring that your test be chemically active. Most tests have expiration dates listed on the box they come in. Make sure yours is still within the useable period. If it is not you will get meaningless results.
    Keeping organic loads to a minimum is paramount to avoiding outbreaks of Cyanobacteria. The techniques to do so have been outlined. Adding potassium permanganate several times a week will keep all blue-greens out of the tank. Of course, efficient skimming is necessary as well and don't forget to siphon out as much as you can.
    jhnrb, Sep 29, 2005
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