"Mr Bond, you return with the tedious inevitability of an unloved season"
Hugo Drax
It's week 146 and it's time for an update of my increasingly inaccurately named blog. I have spent the last 20 weeks waiting for a return of my cyanobacteria problem, and my patience has been rewarded. The difference is that this time I was expecting it. As a result I don't have to trawl through my photos to find rare shots of the tank, or take stills from videos, in order to show the epidemic develop. I have photographed the tank before every weekly tap water change, and measured nitrate and pH. So I have a pretty accurate record of the incidence of cyanobacteria in my tank, as well as at least one variable (nitrate) often quoted on tropical fish forums as being important in determining the incidence of cyanobacteria in fish tanks. So, hold on to your hats.
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| Week 126. The best of times. |
Looking back, this was the best the tank had looked since week 80. The plants and gravel are cyano free, but notice the brown patch on that Amazon Sword plant? It looks like a patch of dead cyanobacteria and I expected it to peel away and be easily syphoned off.
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| Week 129. |
But it didn't peel away, in fact it seemed to slowly spread so that by week 135 some of the leaves were completely covered. This new brown organism also grew in the Java Moss.
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| Week 135. |
Week 135 also was the time I started to observe an increase in cyanobacteria numbers. There had always been sporadic localised outbreaks, but they were easily ignored. In the photo below the brown organism is growing alongside what looks a lot like species 2 (see Chapter XIV) in the Java Moss.
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| Week 135. |
I suspected that the brown organism was species 3 from Chapter XIV because species 3 had such dark pigment. Some microscopy was in order so I took a sample from the Java Moss that had some of the brown material and some of the blue/green.
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| Unicellular organism alongside a filamentous cyanobacteria species (possibly Lyngbya) from a freshwater aquarium. |
The filaments are familiar and look exactly like species 2 but I was not expecting to see the single celled organisms. So, what are they?
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| Higher magnification suggests that unicellular cyanobacteria are present (possibly Chroococcus and Pleurocapsa species). |
They are cells that obviously reproduce by binary fission but that do not form chains. There looks to be multiple forms in this sample, note the groups of four cells (arrowed). They appear to contain a pigment and that pigment is distributed evenly throughout the cell. Their pigment is a different colour to the yellowy pigment of diatoms. I think they're cyanobacteria. And if I search
phycokey I can find some similar looking
unicellular colonial cyanobacteria. So it seems that a new species of cyanobacteria appeared in my aquarium. It is capable of forming mats and has a definite preference for growing (very slowly) on plants.
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| Week 126 |
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| Week 129 |
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| Week 133 |
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| Week 136 |
I say "new" species of cyanobacteria but I suspect it has always been in the tank. I had probably never noticed it before because I, like most fish keepers I think, always assume that a brown coating on plant leaves is diatoms (brown algae). But I think I can say I have never noticed it in the quantities seen by week 136. So it seems that the die-off of species 1 (see Chapter XI), and general reduction in cyanobacteria I observed between weeks 112 and 120 stopped at some point. Conditions for cyanobacteria seem to have improved and this resulted in the visible appearance of a new cyanobacteria by week 126. But, apart from the brown leaves, the tank looks great so it wasn't a problem in fish keeping terms. I didn't feel at this stage that there was enough cyanobacteria in the tank to test if using aged water (AW) does have an effect on cyano, but I did think the tank was heading in the right direction for such a test to be done.
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