Chapter 21. Does using aged water reduce cyanobacteria in my aquarium?

If using aged water (AW) did reduce the amount of cyanobacteria in my aquarium, if it is really was the factor responsible for the reduction I observed in Chapter XI, then I would expect it to do so reproducibly and over a similar amount of time. In Chapter XI I noted that I observed a dramatic reduction within five weeks, so for me to be convinced this time I would have to see a dramatic reduction over a similar timescale.

Week 148. Cyanobacteria (possibly green Lyngbya mats and brown unicellular cyanobacteria mats) from a freshwater aquarium. Photo taken Immediately before the first AW change.

As you can see, by week 148 species 2 was growing well on the Moss Ball and Amazon Sword but also on the tank walls, bog wood and gravel (the gravel was more affected at the far end of the tank). As I mentioned in Chapter 19, I was pretty efficient at removing it from the plants at this point and ruthlessly efficient at removing it from the tank walls and gravel, so most of what you see here will have grown in the week since the last water change.

Week 154. Immediately before the seventh AW change.

I could argue that there was less cyanobacteria in the tank at this point but I can't claim that the reduction had been dramatic. The bogwood was still almost covered and the Moss Ball. There was still cyanobacteria on the gravel and tank walls.

Week 154.

I think the best I can say is that the cyanobacteria problem hadn't got any worse, which is something because in my experience cyanobacteria problems always get worse. But there was little evidence that using AW is worthwhile. It occurred to me that one reason why it had failed might be the condition of the container I age my tap water in.

Week 149.

The inside had become almost entirely coated in a slimy layer of what I assume to be bacteria. So in an attempt to replicate the conditions when I first used AW and the container was new, I gave it a really good clean with a bottle brush and continued the weekly AW changes.

Week 160.

I think it's fair to say that over the next six weeks there has been a dramatic reduction in the amount of species 2. There is still some on the bogwood and gravel, but the plants are mainly clear, and there is none on the tank walls. Interestingly, the colonial unicellular cyanobacteria has returned on the Amazon Sword leaves. It's like the cyanobacteria succession I saw in Chapter 19 is happening in reverse. If that is true then over the next few weeks I should see a reduction in the brown unicellular mats. At that point I will switch back to fresh tap water in the expectation of seeing the succession played out once more.

Chapter 20. Cyanobacteria identification 6 (species 2 and 3)

This is mainly as an excuse to post more microscopic images of cyanobacteria, but I thought I would explain why I have started calling species 2 "possibly Lyngbya" and attempt to identify species 3.

Three filamentous cyanobacteria from a freshwater aquarium. Identified by an amateur at the genus level as;  Lyngbya (thick filaments), Jaaginema (sinuous filaments), and Romaria (short filaments).

From Chapter XIV (where I wrongly identified species 1), I know that species 1 is 2 micrometers wide because I measured some filaments under the microscope using eyepiece and stage graticules. By my calculations, depending on which photo I take measurements from, species 2 is somewhere between 8-10 micrometers. So, using the same key I used to more accurately identify species 1 in Chapter XVI, we get.

Q1. Are the filaments 3 micrometers wide or more?  A-Yes. Q2. Are the filaments cylindrical, long, sometimes constricted at the cross walls, but cells not barrel shaped or sub-spherical? A-Yes. Q3. Are the cells short, always shorter than one half the cell width? A-Yes. Then we come to the crunch. Q4. Are the filaments in vegetative state always without sheaths (if present formed only under stress)? Sheaths again! The problem is that the species 2 sample I examined in Chapter XVI  which showed clear evidence of sheaths, could have been stressed because it had sat around for a week. So I examined a fresh sample.

Filamentous and unicellular cyanobacteria from a freshwater aquarium.

No evidence of sheaths in this sample, but note the dark stripes along the filaments, it is at these necridia that the filaments fragment. I added some very small glass beads to the sample and vortexed briefly. The idea was that if I damaged the filaments I might see evidence of sheaths.

Fragmented sample of filamentous cyanobacteria from a freshwater aquarium.

It seems to me that the filaments have fragmented at the necridia. Many filaments now seem to have the remains of necridia at their end. This could happen if the filaments lacked sheaths so it doesn't tell me much.

Diatoms alongside unicellular and fragmented filamentous cyanobactera from a freshwater aquarium.

These fragments don't even have the remains of necridia at there ends. Maybe the fragmentation was too vigorous. What I really need is to slightly damage the filaments. Perhaps in the future I will find a way of doing that. But there is some evidence of sheaths here.

Fresh cyanobacteria sample from a freshwater aquarium showing evidence of sheaths.  Possibly Lyngbya.

So, if it's Q4. A-No to trichomes always without sheaths then it's Yes to "Trichomes in vegetative state always within distinct sheaths (only hormogonia and reproductive trichome segments can be without sheaths)". Q5. Do the filaments contain one trichome per sheath, forming mats? A-Yes = Lyngbya.  Of course it's possible that I have a mixture of species, some with sheaths (Lyngbya) and some without (Oscillatoria).

Possible Lyngbya filaments showing evidence of sheaths.

If you search for pictures of Lyngbya you will find some very similar images to the species 2 photos I have posted in this and other chapters.

Finally species 3. Q1. Are the trichomes less that 3 microns wide? A-Yes. Q2. Are the trichomes without sheaths or within simple, thin sheaths (when present always one trich/sheath) solitary or in mats, trichomes isopolar (both poles with same morphology)? A-Yes. Q3. Are the trichomes without sheaths, but may possess wide or diffuse mucilaginous envelopes? A-Yes. Q4. Are the trichomes straight, wavy, or irregularly coiled? A-Yes. Q5. Are trichomes mainly short, curved or irregularly coiled, usually only few celled, disintegrating , sometimes enveloped by an indistinct wide mucilaginous envelope, neighbouring cells occasionally disorganised? A-Yes (I guess) = Romaria. I can't find any photos of Romaria so I think I'm on shaky ground with this one. Correct me if I'm wrong.

Chapter 19. The rise of the Cyanobacteria.

Week 137

Week 139

So to re-cap. By week 137, 13 weeks after reverting to standard tap water changes, a uni-cellular cyanobacteria had largely covered the Amazon Sword plants and was growing in the Java Moss. There were also small patches of species 2, particularly in the Java and on the Moss ball. It is strange that the Elodea and Hygrophila  seem much less affected. But the cyanobacteria outbreak (if you can call it that) was mainly a plant problem. The gravel and tank walls were largely clear. Then in week 139 the brown colonial mats on the Amazon Sword plants started dying.

Week 141

Week 143

By week 141 they had died right back, this effect was tank wide. I don't know what caused this sudden population crash, or the gradual increase before it. But I may as well state that for the 15 previous weeks the levels of nitrate I measured varied between 0.2 and 1.0 ppm with no general trend I can see. No explanation then for the re-appearance of what I assume are unicellular cyanobacteria on the Amazon Sword, bog-wood and, importantly I think, the gravel (week 143 above). It's also growing on the glass. It is at this point that a cyanobacteria population becomes a problem, because anything that obscures the view or makes the gravel look dirty is an embarrassment.

Week 145

Week 146. 

In week 145 I forgot to photograph the tank before I had cleaned the tank walls. This is why they look clear, but you can see that there are species 2/brown mats on the gravel and the Hygrophila, in fact all the plants are now affected.  Notice how red the brown mats can be, it reminds me of the cyanobacteria seen in reeftanks. By week 146, species 2 was starting to dominate the tank. Nitrate levels had dropped to undetectable for weeks 144-146, but I see no reason to think this has caused the recent increase in cyanobacteria. It could just as easily be a consequence.

If you compare these pictures with the one at the beginning of the previous post, it's clear that cyanobacteria (of one sort or another) have increased dramatically over the last 20 weeks. It's the classic pattern, the more I syphon off, the more grows back. The traditional advice would be to increase the frequency of water changes, or maybe to add nitrate, but I know from experience that would be futile (see Chapter VII).

I would like to make two points about my new cyanobacteria infestation in comparison to the previous species 1 (Jaaginema?) in terms of aquarium maintenance. Firstly; the new species do not smell as strongly. The characteristic smell of cyanobacteria is apparently due to chemicals they produce, mainly geosmin and MIBs. They are said to give cyanobacteria an "earthy smell" but I prefer to think that soil smells of cyanobacteria. In all my reading about cyanobacteria identification and classification I have not seen smell mentioned as a criterea to define genera. Maybe it could be. What I can say is that species 1 (Jaaginema?) produces lots of geosmin/MIBs whereas species 2 (Lyngbya?) and 4 (Unicellular) do not.

Secondly; they are much less sticky (see video). During the first infection, it was very difficult to syphon a species 1 mat off a small plant and impossible to syphon it off the gravel. It would always hang on to enough gravel to weigh it down in the syphon tube. These new species come away nicely. So, the tank doesn't smell and it's easier to remove the new cyanobacteria, but it still gives the tank that primordial vibe. I prefer the verdant green spotless tank of week 126 so I will try and reduce the cyanobacteria in the same way as described in Chapter XI.

Chapter 18. Cyanobacteria identification 5. A New Player Emerges.

"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.

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.

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.

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.

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.

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?

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.

Week 126

Week 129

Week 133

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.

Chapter 17. Maybe it was all a coincidence.

It's four weeks on from Chapter XV and it is becoming clear that heating the AW to 70 C before using it for a water change did not result in an increase in cyanobacteria (possibly Jaagenima see Chapter XVI). Not only that, but the same process of gradual die-back has continued. I have made a slideshow covering the period week 114 through 124 focussing on an Amazon Sword plant. It's available on youtube.

The final two stills cover the period after heating the AW, the tank looks better than ever. For the last two changes (week 125-126) I have been using ordinary tap water (it's good not having the hassle of running a second air-stone and heater), and so far no sign of a return either. There's still cyano in there of course.

Week 125.  Cyanobacteria hunting

Waiting, patiently, the only remaining species 1 mat is on the plastic filter housing (top left). There's a little species 1 in amongst the Java Moss as well (it's obvious if your eye's in) and what looks to me like a mixed (species 1/2) fine mat on the bogwood.

Week 125.  Fix bayonets.

The fact that heating the AW didn't result in any increase in cyano might suggest (if you believe what you read in Chapter XIII) that it wasn't the microbial community in the AW that affected the cyano. But the fact that going back to tap water hasn't caused a recurrence means that it is a formal possibility that the whole thing was a coincidence. I don't think I can conclude anything because the fact is my aquarium has fundamentally changed.

1. The pH has lowered from 7.6+ to around 7.2. 
2. Nitrates now accumulate between water changes.
3. The plants are growing.
4. There is a lot less cyanobacteria.

1. As for the pH dropping, I think I made a big mistake in Chapter XII. I measured a drop in tank pH in week 115 it's true but, looking back at the calender I write all my tank notes on, I see that I first recorded a drop in tank pH in week 111, one week before the first AW change. It seems that this slipped my mind when I wrote Chapter XII. So the statement " It seems maturing my tap water for a week results in a lowering of its pH. And that by using it for water changes I have lowered the pH of my tank" was wrong. I don't know why the pH of my tank dropped and I don't know when because the closest pH reading I can find is 7.6+ in week 37. I gave up measuring the pH back then because it was always the same. Maybe the death of the Cardinal in week 115 suggests the pH drop had been recent. Or maybe the cardinal just died.

2. As I said in Chapter VII, at the height of my cyano problem levels of nitrate dropped between water changes even though I was adding KNO3. At the time (week 50) I gave up testing for nitrate because I had decided that nitrates and phosphates didn't have any effect on my cyano problem. I started testing again in week 115. Levels were close to zero and remained so until week 117, since then they have tended to increase. These last few weeks they have been around 1-2.5ppm. The simplest explanation of this would be that the cyano was using up a lot of nitrate, but that might not be the only reason. 

3. As you can see from the slideshow, the cyano die-off has had a dramatic effect on the plants. They're all growing, but the Amazon Swords are growing well. The mats that covered them were on both sides of the leaves so I'm amazed they survived. Amazon Swords are the ultimate low light plant.

4. I don't bother cleaning the remaining cyanobacteria any longer. Live and let live I say.

Whatever the cause, the change has been dramatic. It's like a totally new aquarium with a different balance of organisms, a new ecosystem if you will. One of the most dramatic changes is the amount of algae. I used to get some green spot algae on the tank walls (especially the back wall). As you can see from the slideshow, the green spot turned orange, then brown and was easily scraped off with a scouring pad on a stick. I haven't seen any green hair algae since I stopped adding nutrients. And yet I'm testing positive for nitrates, so by definition there must be an excess in my aquarium. It seems that the changes in my aquarium that disadvantage cyanobacteria also disadvantage green algae. Of course all this has made my life a lot easier. Cleaning the tank takes about 5 minutes and I can do a water change in 45 minutes. It used to take hours.

However, intellectually this is most dissatisfying. I have no idea what caused my cyanobacteria outbreak, and I am uncertain what solved it. The whole point of starting this blog was to say something sensible about the causes of cyanobacteria problems and to provide some advice that was based on reason. All that is left to me is to speculate.

It's possible it was all a coincidence, but it's also possible that using AW for ten weeks (weeks 112-122) set in motion a chain of events that could not be reversed by going back to tap water. I imagine it's possible that once the ecology of an aquarium changes, once new species become established, the previously dominant species can never naturally take over. Maybe if I'd gone back to tap water after five weeks I would have seen a recurrence. But I got spooked by the Cardinals demise, I didn't realise the pH of my tank had already dropped. There is a way to test my theory. If I have learn't anything about the causes of cyanobacteria in my fish tank, I should be able to trigger an outbreak by dosing with antibiotics. This should convert the tank to a state that previously has favoured the dominance of cyanobacteria after using tap water for changes. I would be very interested to know the effect that would have on tank pH. If the cyano returned I could then test if using heated AW could reduce the cyano, and if it didn't, I would be able to repeat the observation that AW did reduce cyano. It's Christmas eve tomorrow and I am in no mood to start a cyanobacteria outbreak, but in the new year, if I don't see any return after 10 weeks of tap changes, I'll think about it.

Chapter XVI. Retraction of chapter XIV and cyanobacteria identification 4

I know that the the world is an extremely volatile place, but nothing could have prepared me for the turmoil I discovered in the world of cyanobacteria classification. My mistake had been not to check how up to date the taxonomy keys I was using were. I now know that if you want to identify your cyanobacteria with more recent information the book to read is Freshwater Algae of North America: Ecology and Classification. By John D. Wehr and Robert Gordon Sheath. It contains a new key as of 2003. It seems that the previous system didn't consider enough consistent filament features and paid too much attention to features that tended to vary. As a result, during the 1990s/2000s, the thin (less than 3 microns) filamentous, non-heterocystous cyanobacteria were completely re-classified. Oscillatoria splendida and O. amphibia were removed from the genus Oscillatoria and into a new genus Geitlerinema. Not only that but the genus Geitlerinema is one of eight in the family Pseudoanabanaceae and the thin filaments had been distributed amongst them. At first I thought it would be no problem. I would find out the new names for O. splendida and O. amphibia. Then when I searched for information about them I would get the latest. Maybe then I could answer my questions:

1. Has my species 1 been found in cyanobacterial blooms in nature? 
2. Does it produce toxins?
3. Can it fix nitrogen?
4. Is it common in the environment/water supply?

It turns out O. splendida and O. amphibia are now called Geiterinema splendidum and G. amphibium but  one of the defining characteristics of the genus Geiternema is that the filaments exhibit "intense longitudinal gliding". I know what they mean by that because when I first examined the mixed sample from the moss ball (Chapter XIV) the species 2 filaments were moving out and into the field of view like freight trains. The species 1 filaments gently waved at the ends and it looked like there was some rotation to the movement but it was not longitudinal. As a result I can safely say I wrongly identified species 1 in Chaper XIV because filament movement  is one of the new genus defining features. So if it wasn't a Geiterinema sp. which of the other seven genera was it? I was back to square one but I had a new key to follow. I went back to the original photos and looked at them more closely. I'm going to ignore the filaments with one tapered end and one rounded (heteropolar filaments) for now. (Edit 7-9-14 see Chapter 22 for an update on the issue of longitudinal gliding.)

Picture A. Cyanobacteria species 1. Thin (2 microns) filament showing the 'granules'  at the cell junctions (arrows)

Things start off easy enough. Q1-Are there heterocysts? No. Q2-Are the filaments less than 3 microns wide? Yes. Q3-If the trichomes have sheaths, are the sheaths thin with one trichome per sheath? Yes. Q4-Do the trichomes have thin, fine or firm sheaths? I had to give this question a lot of thought. If I look at almost any photo of species 1 I can see a brownish layer round the outside and sometimes a thin diffuse light diffracting layer around that. Many species of cyano produce a sticky layer around their filaments called a mucilaginous layer. It helps then form matts. But is that what I see? or is it a thin sheath? The problem is, if I answer yes I end up at a genus that looks a lot like species 1. Here is a photo of a Leptolyngbya species from a website that is run by scientists so it should be trustworthy. The gaps between the cells in this photo remind me of my filaments and Leptolyngbya are defined in the key by their ability to form mats which mine certainly can. Looking at this photo I have to say that if these filaments have sheaths then maybe so do mine, they look 'as sheathed' if you know what I mean. However, in the description of the linked photo it says "Filaments sometimes lacking sheath material" and "Sheath highly variable in thickness" which contradicts the key as Leptolyngbya are supposed to have 'thin, fine or firm' sheaths.

Picture B. Cyanobacteria species 1 filaments showing  gaps between cells

Here is another Leptolygbya photo, again from academics. The description regarding sheaths is "Sheath thin, colorless, usually diffluent, indistinct, mucilaginous, rarely distinct". So maybe my filaments do have a thin mucilaginous sheath. For me, a sheath has to be a separate structure from the trichome. Here is a photo of species 2 from the moss ball in Chapter XIV

Picture C.  Cyanobacteria species 2 filaments showing the clear sheath

All my other cyano photos are from fresh samples examined within hours of sampling. This photo was taken after the sample had sat in a tube for a week. Because some of the trichome cells have died you can clearly see the sheath. Compare that with species 1

Picture D. Species 1 filaments apparently lacking sheaths but having a thin mucilagenous layer (small arrow). The process of filament fragmentation without necridia may be occurring (large arrow).

The only thing holding these two four celled filaments together is the two dead cells between (large arrow). The thin diffuse layer around the trichome does not extend to the dead cells so that's no sheath in my view. It's a coating that the living cells seem to exude but that doesn't behave as a cohesive structure. So I'm going to answer no to Q4. Q5-Are the trichomes straight/wavy/irregularly coiled? Yes. Q6-Are the trichomes cylindrical and multi-celled without wide mucilaginous envelopes? Yes. Q7-Are the filaments solitary or in fine colonies and are the trichomes constricted at the cross walls, sometimes with polar aerotopes? I don't think I could describe the mats that used to cover my tank as 'fine colonies' and I don't think the trichomes are constricted at the cross walls either. But what about polar aerotopes? An aerotope is a collection of gas vesicles which give some species of cyanobacteria buoyancy. They can regulate how much gas is stored and so move up and down in the water during the day. As you can see from all three of the species 1 photos in this post, the cells in my filaments contain objects.

Enlargement of Picture A. Cyanobacteria species 1

These two enlargements are from Picture A. I think the fact the objects look pale at the top of the filament and dark at the bottom is a trick of the light. Could these be polar aerotopes? They do seem to be mainly at the ends (poles) of the cells. Here is a photo of  Limnothrix redekei a species which has polar aerotopes. Unfortunately you can't zoom in but if you download the picture and have a good look you will see that aerotopes seem to vary in size. I've read that some can take up 50% of the cell. The objects in my filaments all look roughly the same size. So if it's no to Q7 then it's yes to "Trichomes in larger clusters/mats, not constricted at the cross walls. No aerotopes but scattered or polar granules". Q8-Are the filaments motile? No, not if they mean 'intense longitudinal gliding' and I think they do because if I answer yes I get Geitlerinema. So in conclusion, my new best guess is that my tank was overran by a species from the genus Jaaginema. There are very few photos of Jaaginema I can find and some of them I think have been wrongly identified because their cells are thinner than the trichomes are wide and the trichomes look to be >3 microns wide. I find quite a lot of wrongly captioned photos of cyanobacteria, this is why I don't include genus or species names in my photos. Here is a link to a photo of a Jaaginema species that looks similar to my filaments, allowing for the fact that they seem to have used a fluorescent light source for the photo. And here is the description of Jaaginema from cyanodb, a website run by the guys who reclassified these thin filamentous cyanobacteria.

Descriptions:Komárek (1992): Filamentous; filaments usually solitary or freely clustered (tangled and coiled) into small colonies, rarely forming macroscopically visible mats; trichomes always without sheaths, cylindrical, isopolar, usually wawed or coiled, narrow, thin, 0.5-3 μm wide, uniseriate, usually not narrowed to the ends, slightly constricted or unconstricted at the cross walls, always immotile. Cells cylindrical, elongated, longer than wide (up to several times), without aerotopes, sometimes with solitary granules (rarely at the cross walls); end cells rounded_or narrowed, pointed or conical – rounded, always - without calyptra. Cell content pale blue-green, grey, yellowish or olive-green; in some species ability of chromatic adaptation (changeable phycobiline ratio).
Reproduction strategies, life cycles, cell division:Komárek (1992): Cell division by the crosswise binary fission, perpendicularly to the long axis of a trichome, daughter cells grow +/- up to the original size before the next division. All cells capable to divide. Reproduction by the fragmentation of trichomes without necridic cells into immotile hormocytes (indistinct motility was not proved yet).
Ecology, ecophysiology, ecological significance:Komárek (1992): Mainly benthic organisms, growing on the bottom of diverse water biotopes, pools, lakes, reservoirs with rich vegetation of water plants, commonly in metaphyton. Several species known from mineral, thermal or salinic waters.

Most of this info fits with what I see although "always immotile" is a worry as the filaments from the tropical tank and goldfish tanks did wave about as I mentioned in Chapter XIV. Perhaps "rarely forming macroscopically visible mats" suggests that this cyano behaved unusually in my tank if it is a Jaaginema.  I notice "end cells rounded or narrowed, pointed or conical - always without calyptra" means I don't have to worry about filament ends any more (this must be one of the features they stopped using to classify these species). Calyptra are thickened or enlarged tips to a filament, they can be hood-like, lid-like, or cap-like and I can't see anything like that. Mainly benthic means that this genus usually lives on the bottom of water bodies, usually freshwater. Uniseriate just means the cells are in a single chain. Jaaginema is a little known genus with  27 species according to cyanodb. The question is, if I now search for information on these 27 Jaaginema species (and their previous names from the Oscillatoria days) will I be able to answer any of the questions I listed at the start of this post?

Chapter XV. The effects of heating water on pH

I'm taking a break from taxonomy to provide an update on the experiment I described in Chapter XIII.  After writing "This should kill 99% of bacteria etc. but I think leave the water essentially unchanged" it occurred to me that I better look into what the likely effects of boiling water before adding it to an aquarium might be. There is very little information I could find, especially relating to fish keeping. But the always dependable Skeptical Aquarist has an article on using boiling to soften water. The linked article predicts that the water will be depleted in dissolved oxygen and may have lost some of its buffering capacity. I decided to test what the effect of heating my tap water (TW) was. I heated 15 liters of TW to 70 Celsius in a stainless steel stockpot. I measured the pH before heating and after. I then added an air stone and left it for one week, taking daily pH readings. As I described in Chapter XII, leaving my TW for a week results in a slight reduction in pH. I assume this is the result of the aerobic respiration of organisms present (see here for a great article on bio-acidification). If my heated TW had lost buffering capacity then I might expect to see a more dramatic reduction in pH than in the AW as a population of microbes developed. I went for 70C because I didn't wan't the water to bubble and drive off too much dissolved gas but I should still kill most microbes when the time came to repeat  the process for real on the AW.

TW 0h

Heated TW 70 C + 16h

Heated TW 70 C + 6 days

As you can see, either heating the TW reduced its pH or leaving it overnight has (I should have bought two stockpots, filled them both with water and only heated one of them :). There doesn't seem to have been any further drop in pH during the week so no evidence of a reduction in buffering capacity. The drop in pH is about the same as I see in the AW. Given that this heated TW must have been low in microbial life and has dropped in pH within 16 hours, it does make me wonder if bio-acidification is responsible for the reduction in pH I see in the AW. Maybe its a chemical process. To test this I measured the pH of a sample of tap water straight from the tap and filled a saucepan, left it for 30 minutes and measured the pH.

TW 0h

TW 30m

There's a clear difference and the 30 minute sample looks to be about the same pH as the heated TW after six days. I would guess the process is chemical as 30 minutes seems too fast for a biological process. My explanation would be that water for domestic use is pumped around under pressure. When I fill a container with it the water equilibrates to atmospheric pressure and gaseous exchange takes place. In my case this seems to result in a slight drop in pH (which may suggest that CO2 is being absorbed). The pH then seems to remain stable. I haven't been able to find much information on what the likely effect on pH of storing water would be but here is a link where they measure an increase in pH over 12 days. In the discussion they say "The observed increases in pH during storage could be due to the activities of the resident flora and or their death, which results in the release of inorganic substances such as ammonia". This doesn't seem to be happening with my water. My question is: what were the processes in my aquarium that had previously conspired to maintain the tank pH 7.6 or above while the water I was adding naturally drops to a pH below that after adjusting to atmospheric pressure? As I mentioned in Chapter XIII, I had never measured tank pH lower than 7.6 in the entire two years and three months of cyanobacteria. Anyway, I was satisfied that heating my water to 70C doesn't have a dramatic effect on its pH so I repeated the process on AW and used it for a water change today.

AW 6 days

AW 6days 12 hours after 70 C

It took 30 minutes to heat up the 15 litres of AW and eight hours to cool from 70 C - 20 C. To achieve this rate of cooling I left the stockpot outside on a cold day. When I got back from work I added a heater and an airstone for an hour or so to add some oxygen and warm it up to tank temperature (23 C). As you can see, heating the AW doesn't seem to have affected its pH as predicted. After the water change the fish seemed fine. Now I play the waiting game.