As I wrote in
Chapter 22, by week 196 I observed filamentous cyanobacteria had returned to my freshwater tropical aquarium. I felt there was enough of it to test the ability of aged water (AW) to reduce its abundance. To re-cap, I had previously observed two occasions where the use of AW had apparently led to a reduction in the abundance of cyanobacteria. Firstly in
Chapter XI (W112-W120) where I saw a dramatic reduction within five weeks and almost complete disappearance within eight, and again in
Chapter 21 (W148-W160) where I observed a dramatic reduction in 12 weeks. In order to replicate the conditions when I first used AW I used a brand new water container to mature the water.
I have to say, I was pretty confident it was going to work. And this third test would have been sufficient to convince me that keeping 20 litres of water heated to tank temperature and aerated for a week prior to adding to the tank was an effective way of controlling cyanobacteia (in my aquarium at least).
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| W197. Photo taken before the fist aged water (AW) change. The tank is in the early stages of a mixed Geitlerinema/Lyngbya infestation. |
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| W209. Photo taken before the twelfth aged water (AW) change. The tank is dominated by a Lyngbya infestation. |
However, it's obvious from the photos above that on this occasion, using AW has not resulted in a reduction in the abundance of cyanobateria in the tank. Indeed, the cyanobacteria problem has got much worse during the 12 weeks I used AW. Consequently I have to conclude that there is no benefit in using AW. This raises the obvious question, what was the reason for the dramatic decline in cyanobacteria abundance I observed between weeks 112-120 and again in W148-W160? And why were both these episodes followed by long periods where filamentous cyanobacteria were rare? The only macroscopically visible cyanobacteria in the aquarium were the brown unicellular types for 26 weeks following W120 and for 31 weeks after W165. Given that its disappearance seems to have nothing to do with using AW (and equally that its reappearance has nothing to do with using fresh tap water), I have to admit that after four years I am no further forward in understanding the causes of my cyanobacteria problem. Although I note the problem has changed subtly. During the first two years and three months the tank was in existence, I can't remember any occasions where the cyano died back spontaneously as it seems to have twice here. It is the cyclical nature of my current cyanobacteria problem that interests me. So my plan is to do absolutely nothing new and see if the cycle repeats. When that might be is unclear.
