# Does Alkaline Water Favour Cyanobacteria (aka BGA)?



## jaypeecee (17 Mar 2021)

Hi Everyone,

Some of you will know that I have taken an active interest in Cyanobacteria (aka BGA). The reason for this is simple - I have had several infestations of this unwelcome guest in my tanks over the years. So, I tend to avidly read any new research that I find on what I refer to as the 'Blue-Green Menace'. It was therefore with some curiosity that I discovered the following scientific research:









						pH determines the energetic efficiency of the cyanobacterial CO2 concentrating mechanism
					

Cyanobacteria are responsible for roughly 10% of global photosynthetic primary production of reduced carbon. Although cyanobacteria are incredibly diverse, all known species contain a complex protein system called the CO2 concentrating mechanism (CCM), which enables rapid growth even in...




					www.pnas.org
				




Having read what I could understand of the above paper, it seems to me that Cyanobacteria may prefer to inhabit alkaline water. And, since my tanks inevitably tend to have water in the pH region from 7.0 to 8.0, this has piqued my interest. Am I barking up the wrong tree or is there something of relevance here?

NOTE: To keep things simple, the first paragraph of the Discussion section was the important bit for me!

Any feedback welcome!

JPC


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## hypnogogia (17 Mar 2021)

Interesting question.  I've only ever had BGA once, and that was years ago when I used exclusively tap water and no CO2.  My water then was alkaline.  my most recent tanks have always used rainwater cut with some tap and CO2, so tend to be below 7ph.  Never had BGA again.  This could of course be pure coincidence.


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## jaypeecee (17 Mar 2021)

Hi @hypnogogia 

Thanks for the feedback.

JPC


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## jaypeecee (26 Jun 2021)

Hi Folks,

For any of the UKAPS members who own a calibrated pH meter, it would be interesting to know if your tank(s) succumb to cyano (aka BGA) problems. The question is:

_Do your tanks have visible cyanobacteria and what is the (range of) water pH in your tanks?*_

I'm under no illusion here - water pH is just one of many factors that are related to the growth of what I call _The Blue-Green Menace_.

* If you are using CO2 injection, there will be a minimum pH and maximum pH.

JPC


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## MichaelJ (27 Jun 2021)

Hi @jaypeecee, Interesting. Way in the past when I was keeping a lot of South American Cichlids (mostly incredibly messy but highly entertaining Ciclasoma's) I had BGA all the time - these were very lightly planted (if at all) and brightly lit tanks. The water I used back then was straight tap with a pH in the 7.6-8.0 range as far as I remember.

In my current two low-tech densely planted and dimly lit tanks I have no algae of any kind to speak of. Last time I checked with a calibrated probe pH was around 7.2 - 7.4 in both.

EDIT: I do not know exactly what the cause and effect is here, but if I had to guess, it might have to do with high light levels and low nitrate levels in the cichlid tank vs low light and high nitrate levels in the densely planted tank?  I was always under the impression that low nitrate levels could trigger BGA outbreaks. 

Cheers,
Michael


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## jaypeecee (27 Jun 2021)

MichaelJ said:


> I do not know exactly what the cause and effect is here, but if I had to guess, it might have to do with high light levels and low nitrate levels in the cichlid tank vs low light and high nitrate levels in the densely planted tank? I was always under the impression that low nitrate levels could trigger BGA outbreaks.


Hi @MichaelJ

There's little doubt that 'high' light intensity accelerates the rate at which all species of cyano grow. The low nitrate issue is not so clear cut from the scientific papers that I have read. The _ratio_ of nitrate to phosphate (or nitrogen to phosphorus) may be more relevant. I have extracted the following from such a paper:

"Many times, the proportion of N and P in aquatic ecosystems are observed as N to P ratios, where aquatic ecosystems with low N to P ratios tend to favor dominance by M. aeruginosa and other cyanobacteria". *

In other words, it's not the _absolute_ amount of nitrate that's critical.

JPC

* Master's Projects and Capstones | Theses, Dissertations, Capstones and Projects | The University of San Francisco


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## MichaelJ (27 Jun 2021)

jaypeecee said:


> Hi @MichaelJ
> 
> There's little doubt that 'high' light intensity accelerates the rate at which all species of cyano grow. The low nitrate issue is not so clear cut from the scientific papers that I have read. The _ratio_ of nitrate to phosphate (or nitrogen to phosphorus) may be more relevant. I have extracted the following from such a paper:
> 
> "Many times, the proportion of N and P in aquatic ecosystems are observed as N to P ratios, where aquatic ecosystems with low N to P ratios tend to favor dominance by M. aeruginosa and other cyanobacteria". *


Hi @jaypeecee  I've never paid attention to ratios only absolute levels of NPK - never thought it had any significance compared to say proper light levels, WC and general cleanliness of the tanks and overall bioavailability of fertilizer (in that order). There was a recent discussion on NPK ratios here.
I run my planted tanks at high levels of NPK. Nitrate in the 40-80 ppm range (API test)... Phosphate in the 40 ppm range (Maxes out on the API test scale... so I don't know for sure) and K in the 70-80 range. My Phosphate level is estimated based on dosing and my K level based on use of Potassium softened tap water / RO Mix. Perhaps ratios plays a role at lower or scarce levels of NPK - I do not know?  Of course, this is all anecdotal and my experience may be an outlier - I doubt it though. I will read the paper as I am always _all ears_ when there are good science papers relevant to the hobby.

Cheers,
Michael


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## glasscanvasart (27 Jun 2021)

I’ve had it in a few set ups now. What I’ve associated it with is low nutrients, low flow and detritus. Detritus seems to be the biggest of the three conditions followed by nutrients. The cure has been EI dosing, water changes and manual removal, but I’m sure more flow also helps.


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## MichaelJ (28 Jun 2021)

glasscanvasart said:


> I’ve had it in a few set ups now. What I’ve associated it with is low nutrients, low flow and detritus.


@glasscanvasart   Totally agree. I forgot to mention proper filtration above - which includes flow. Very important regardless.
Cheers,
Michael


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## jaypeecee (28 Jun 2021)

MichaelJ said:


> I will read the paper as I am always _all ears_ when there are good science papers relevant to the hobby.


Hi @MichaelJ 

There are some very informative scientific papers and other resources out there dealing with cyanobacteria. I have accumulated quite a few of these. There are so many interacting factors that play a part in the growth of cyanobacteria. Although my background is in the Physical Sciences, I am enjoying my exploration of the Life Sciences. I am having some success controlling cyano. This may be of some interest to you:





__





						Cyanobacteria Identification - At Last!
					

Hi Folks,  Like many other aquarists, I have had cyanobacteria (aka 'BGA') grow in my tanks. And I started reading about this stuff. Of course, I initially thought BGA was algae. Why else would it be known as BGA (Blue-Green Algae)? But I later discovered that it's not an algae at all. It's a...



					www.ukaps.org
				




JPC


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## jaypeecee (28 Jun 2021)

glasscanvasart said:


> What I’ve associated it with is low nutrients, low flow and detritus.


Hi @glasscanvasart 

From what I've read, it would appear that low nutrients isn't correlated with the growth of cyanobacteria. But, it depends to which nutrients we are referring. For example, detritus can probably supply all the nutrients that cyano require. However, low flow is probably a factor as it permits certain species of cyano to settle on the substrate where the individual filaments of, for example, Oscillatoria can clump together. Here, they can take advantage of some nutrients that leach from the substrate. There are also quite a few scientific papers that discuss the relative ease with which cyanobacteria grow in alkaline water in preference to acidic water. I have an experiment running at the moment in which I'm putting this to the test.

To be continued...

JPC


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## glasscanvasart (29 Jun 2021)

Interesting what you say about flow and the formation of Cyanobacteria colonies. Makes a lot of sense since they are basically an agglomeration of tiny bacteria. Having said that, I have a no flow / filtration set up, that was infested with Cyanobacteria and what seemed to tilt the balance was EI dosing, water changes and detritus removal rather than flow.


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## jaypeecee (1 Jul 2021)

glasscanvasart said:


> I have a no flow / filtration set up, that was infested with Cyanobacteria and what seemed to tilt the balance was EI dosing, water changes and detritus removal rather than flow.


Hi @glasscanvasart 

Interesting. The water changes and detritus removal would have reduced the dissolved organic matter (DOM) in the water column. By definition, DOM contains carbon but is very likely to also be a source of nitrogen and phosphorus, which feeds algae and cyanobacteria (BGA). Unlike detritus, dissolved organics are just that - _dissolved_ and not readily visible.

JPC


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## sparkyweasel (31 Jul 2021)

Hi @jaypeecee 
I came across this paper when I was looking for something else, and thought you might be interested if you haven't come across it already.
It suggests that humic substances inhibit cyanobacteria more than they inhibit green algae or macrophytes.
As humic substances are usually associated with acid waters this could be the other side of the coin.
Dissolved Humic Substances . . . Steinberg et al, 2006.
Link

I notice Wetzel gets a mention;
"We dedicate this paper to the memory of Profs. Robert G. Wetzel and Richard C. Playle . . ."


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## MirandaB (31 Jul 2021)

I'm having real problems with Cyano at the moment and it's only in my temperate tanks with very good flow and no plants 
None have strong lighting and one is only lit by natural light,ambient temperatures seem to be a major factor with it in these tanks.


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## jaypeecee (31 Jul 2021)

MirandaB said:


> I'm having real problems with Cyano at the moment and it's only in my temperate tanks with very good flow and no plants
> None have strong lighting and one is only lit by natural light,ambient temperatures seem to be a major factor with it in these tanks.


Hi @MirandaB 

In order to eliminate a few variables, do you have the following measurements for your tank:

(1) pH
(2) Nitrate
(3) Phosphate
(4) Ammonia
(5) Nitrite

That'll do for starters.

JPC


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## jaypeecee (31 Jul 2021)

sparkyweasel said:


> I came across this paper when I was looking for something else, and thought you might be interested if you haven't come across it already.
> It suggests that humic substances inhibit cyanobacteria more than they inhibit green algae or macrophytes.
> As humic substances are usually associated with acid waters this could be the other side of the coin.


Hi @sparkyweasel 

Thanks.

I do have a copy of that paper and it is interesting. When it comes to dissolved organics and humic substances (HS), Steinberg seems to be the foremost researcher in these fields.

I've done one or two experiments with HS but I'm not a fan of water that looks like tea (without milk). I realize that it's perfectly natural for some biomes.

JPC


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## sparkyweasel (31 Jul 2021)

jaypeecee said:


> I'm not a fan of water that looks like tea



Neither am I; in some tanks I use catappa leaves and alder cones in moderation, but not enough to noticably tint the water. 
I have tried tea-dark water but I didn't grow to like it.


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## jaypeecee (31 Jul 2021)

sparkyweasel said:


> I have tried tea-dark water but I didn't grow to like it.


Hi @sparkyweasel 

I'm sure there's a joke there - somewhere. Tea - Grow - Ceylon?

JPC


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## MirandaB (31 Jul 2021)

jaypeecee said:


> Hi @MirandaB
> 
> In order to eliminate a few variables, do you have the following measurements for your tank:
> 
> ...


 Hi @jaypeecee  I'll get those for you tomorrow,I'll take readings for each of the 3 tanks that have it in.


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