Chapter VIII. Cyanobacteria control by eliminating direct sunlight

It was a desperate time. I can remember using a toothbrush to remove a continuous sheet of cyano from the back wall of the tank in one go, I wish I had filmed it. Honestly, the biomass was awesome.

In chess they say it's better to have a bad plan than no plan at all. I thought I would try cutting off the direct sunlight the tank got ( it only got one or two hours a day but I pinned all my hopes on this at the time) and then dosing with antibiotics. In week 57 I installed blackout blinds over the skylights and in week 58 dosed. I gave up adding nutrients, it had been a waste of time and the plants were losing anyway. I just cleaned the gravel and plants and did weekly water changes. As before, back came the hair algae. It seemed like the algae and cyano were in direct competition because knocking the cyano out always caused the algae to grow well. I'll return to this point in a later post. Below are two stills from a video shot in week 62

Week 62. 

The bogwood is covered in hair algae (and cyano) but you can see the gravel is dirty, it was amazing how much fs had built up. The bubbles on the back wall are trapped by the cyano sheet covering the hair algae, this is the cyano equivalent of 'pearling'. So the cyano came back within four weeks, I thought maybe it was getting resistant to the antibiotics and decided to give them up. It was also clear that direct sunlight was not a factor.

From reading the forums it seems that there is an association between localized cyano patches and direct sunlight. The posts are unusual in that the authors often quote their direct experiences. They say things like "I had cyano in my gravel at the front of the tank and it went away after I put black tape over it" or "it goes away if I clean that patch of gravel regularly". I can back this up.

This is a photo of my unheated golfish tank taken recently, it's in a different room but on the same side of the house as the tropical tank. In that bottom corner against the glass is the unmistakable sign of cyano. And that corner gets the most of the one or two hours of direct sunlight. But this is very different to what I'm talking about. The cyano only grows in this corner of the tank and this is four weeks after a water change. It never takes over like it does in my tropical tank. I will examine this cyano  under a microscope and report back, could be interesting.

Back in week 62 I decided it was time to simply accept cyano as my companion.

Chapter VII. Cyanobacteria control by NO3 limitation

"They say the definition of madness is doing the same thing and expecting a different result." 
                                                                                                Howlin' Pelle Almqvist

There are suggestions on the forums that cyano problems can be caused by nitrates being limiting. The idea is that because some species of cyano can 'fix' inorganic nitrogen (N) and convert it to organic nitrates, they have an advantage over other organisms that can't fix N when nitrates are low. But, given that I had no idea if my cyano was able to fix N,  I was in no mood for such thinking. So I thought I would try knocking the cyano out with antibiotics and then dosing with potassium but no nitrates or trace elements. I thought maybe adding nitrates had been part of the problem because I had noticed something strange about my tank. Levels of nitrate decreased between water changes and often became undetectable. This went against everything I had read on the forums. Nitrates were suposed to increase, it was one of the reasons to do a water change. Where was the nitrate going? Given that the fastest growing species in the tank was cyano, this suggested to me that the cyano was using up a lot of the nitrate I was adding, and the nitrate from the nitrifying bacteria in the bio-filter, and the nitrate from the decomposition of fs and dead plants etc. It didn't seem likely that denitrifying bacteria (bacteria that convert organic nitrate to inorganic N) were responsible for the missing nitrate because my understanding at the time was that the anaerobic denitrifying bacteria (bacteria that can't tolerate oxygen) couldn't function in the oxygenated gravel of a UGF. Here is a summary of the N cycle I found.

Adapted from: Mills, D. The Marine Aquarium. Salamander Books LTD.
8 Blenhein Ct., Brewery Rd. London N79NT; 1987.

I stopped adding trace elements because I had read that they, especially iron, can cause cyano problems. I hoped that making the tank more nitrate limited might have an impact on the cyano. At the least I thought it would give me a good run at cleaning the gravel. After a major cyano removal session in week 50 I dosed again with antibiotics. As before things went well to begin with. The cyano died and the tank became dominated by algae and plants.

Week 51. Cyano free but for how long?

I was doing weekly 37% water changes and adding K2SO4. I haven't made a note of exactly when the cyano came back, but I think it was getting serious again within six weeks.
So it seemed that attempting to control the levels of nitrate and phosphate did not effect the growth of the cyano. I'm pretty sure cyano will use added nutrients if they're there, but it didn't seem to depend on them. I am not convinced that the idea that nitrates and phosphates effect or cause cyano problems, comes directly from peoples experiences of fish keeping. I think it comes from the environmental sciences. When I started searching the internet for information about cyano I found a lot of scientific studies of algal blooms in lakes and coastal waters. It seems there is no doubt that nutrient run-off from agricultural land causes cyano blooms in nature. Phosphate is often cited as the main limiting factor for these blooms, and they have been reduced by managing phosphate inputs. One thing that strikes me about these studies is that the blooms are seasonal. I was six weeks into year two of my cyano bloom and it was not seasonal. Maybe I was missing something simple.

Chapter VI-Appendix I. Cyanobacteria identification 1

The face of evil is always the face of total need
William S. Burroughs

After posting Chapter VI it occurred to me to take a sample of my cyano into work, have a look at it under the microscope and take some photos. It's a light microscope, so I couldn't see enough detail to know what species it was. But I could see enough to take a stab at which genus of cyano I had.  A genus is a group of species that all share some common characteristics. I found a website called phycokey (amazing website based at the University of New Hampshire) that helps you identify which genus of cyano you're dealing with based on some pretty obvious features. Here is the link.

This is a low mag view and as you can see my cyano is filamentous (chains of cells not single cells). The filaments are not branched.

This is x400 magnification. You can see that the bluey green pigment isn't confined to sub-compartments of the cells like it would be in an algae (algae can grow in chains as well). That's a good start, I don't have to re-name this blog. The next question you have to answer on phycokey is 'are the filaments tapered?'. From these photos you'd have to say most are not, but maybe I have a mixed cyano population because that filament coming in from right-field is definitely tapered. Anyway, next question is 'do the filaments have heterocysts?'. Heterocysts are specialized cells that enable cyano to fix inorganic nitrogen from the atmosphere. I looked at a load of photos of filamentous cyanobacteria that have heterocysts, and the heterocysts always looked different from the other cells in the chain. These cells all look the same so I'm saying no. Next question is 'do the filaments have a sheath?'. For some cyano that have sheaths, multiple filaments are contained within the sheath and the photos of cyanos where single filaments had sheaves looked nothing like these so I'm saying no. That leaves two possibilities, a group of species where the filaments form spirals or Oscillatoria.

This is a photo from the web of Oscillatoria posted by Paul G. Davison Professor of Biology at The University of North Alabama. I see some of the filament ends are tapered as well. Well i'm pretty happy to call my cyano an unknown species from the genus Oscillatoria. But what does that tell me? In Appendix II I'll post what I have discovered about Oscillatoria species.

Chapter VI. Questions

So, the cyano was not 'self sustaining' after all, nothing is. That was some woolly thinking by me. No matter how much I removed of the slime, how much I diluted it in the water, how low I knocked it down with antibiotics, it would grow back. The conditions in my tank were obviously ideal for its growth. I'm not saying that controlling cyano by phosphate limitation (achieved by stimulating plant and algal growth) doesn't work. I'm just saying it didn't work for me. Maybe I didn't have enough plants/the right types of plants or add enough nutrients. Maybe it works if you have more lights. I note from re-reading the cyano section of The Krib archive that great success has apparently been had using phosphate limitation while adding CO2. But surely it should be possible to have a cyano free tank without injecting CO2! From what I have read the strategy may be flawed anyway. It seems to me to be based on the assumption that plants and algae, the so called 'higher' lifeforms (eukaryotes), are more efficient at phosphate uptake than cyano (cyanobacteria are prokaryotes). I can find no evidence to support this idea, but I can find people who say otherwise.

"Phosphate uptake in cyanobacteria follows saturation-type kinetics with kinetics parameters (K1/2 and Vmax) comparable to those of eukaryotic algae"
Maria del Carmen Avendano and Eduardo Fernandez Valiente. Effect of Sodium on Phosphate Uptake in Unicellular and Filamentous Cyanobacteria. Plant Cell Physiol. 35(7): 1097-1101 (1994)

These scientists have measured rates of phosphate uptake in the lab and basically found cyano and algae take it up at the same rate and with the same efficiency so when phosphate levels are low, neither should have any particular advantage.

"Phosphorus storage in cyanobacteria appears to be much larger than in other species and this capacity was reported to give them a competitive advantage over diatoms and chlorophytes when P was supplied in pulses"
Santosh Kumar Singh, Vandana Pandey, and Kapil Deo Pandey. Phosphate uptake kinetics and its regulation in N2-fixing cyanobacterium Anabaena oryzae Fritsch under salt stress. African Journal of Biotechnology. 6 (20):2363-2368 (2007)

This work suggests that when phosphate is low cyano may even out-compete the algae (diatoms and chlorophytes are algae) because they can store it better. Anyway, this type of speculation is pointless because cyanobacteria are a very diverse group. If you're interested read The Ecology of Cyanobacteria: Their Diversity in Time and Space  it's on google books. They're so diverse that even if you knew which species you had in your tank, you might not be able to predict how they would behave because they vary so much within species. There is a suggestion on The Krib that cyano plagues in fish tanks are "probably Oscillatoria or Lyngbya". I haven't found out if anything is known about the relative efficiency of phosphate uptake in these species, but not knowing what species my cyano is makes it a moot point. It was time for a change of tactic.

Chapter V. Cyanobacteria control with antibiotics

There is a lot of information on the internet about treating cyano infested tanks with antibiotics. Almost always it is pointed out that such treatments only address the symptoms. If the underlying causes aren't dealt with the cyano will come back. My thinking was that I had dealt with the underlying cause of excess nutrients. What I couldn't understand was why the cyano still grew so well. It was as if cyano, once established, was in some sense self sustaining. I thought that antibiotic treatment might knock-out the cyano to a point where the new conditions in the tank meant that it wouldn't dominate. In week 38 I bought a product called cerpofor aerocol No Blue Algae. I disconnected the under-gravel filter (UGF) riser from the power-head but kept the power-head running with its venturi valve open, removed as much cyano as I could and dosed. Three days later I did a 37% water change and reconnected the UGF. I measured 0.1 ppm nitrite (NO2) at this point but levels soon dropped to zero so it seemed my bio-filter (nitrifying bacteria) survived. All the cyano left in the tank had died and was easily siphoned off. I started 37% water changes every five to six days and dosed with potassium and trace elements. As before I added nitrate when levels dropped below 1 ppm. The great thing was, because I wasn't having to siphon cyano off everything, I could devote the full 20 liters to cleaning fs out of the gravel. I stopped using the Algarde and just stuck the siphon tube into the gravel (with a plastic grill to stop gravel going up the tube). It was amazing how much I could remove. It was a glorious time, I remember green hair algae growing on the bog-wood, it got quite long. Eventually back came the cyano. I haven't made a note of the exact date, but I think it was obviously back by week 42 (four weeks on from the antibiotics). Here is a photo taken before a water change in week 49 (11 weeks on).

There are less plants in the tank because cyano seems to effect them eventually. The Ellodea would grow from one end but die faster from the other thus shortening and eventually going yellow and dying. It's hard to know if my cyano produced toxins which affected the plants or if they used up all the nutrients I was adding and so out-competed the plants (search for cyanobacterial blooms in the environmental sciences literature if you're interested in cyano toxicity). The Amazon swords were coated in cyano, but if you removed the slimy film they looked green and healthy underneath. They stopped growing but didn't die like the Ellodea. Maybe the cyano was toxic to the Ellodea but not the Amazon Swords? One thing was certain, the cyano was dominating my ecosystem again.

Nice shot of the cyano on the bog-wood and some Hygrophila polysperma plants I had added to see if they did any better than the Ellodea (week 49 again).

Chapter IV. Cyanobacteria control by PO4 limitation

The problem I had was, I had no idea what the levels of phosphate and nitrate were in either my fishtank or my tap water. Improving circulation hadn't helped. But, I couldn't be sure that by frequently changing the water and vacuuming the gravel, that I was reducing NO3/PO4. So in week 30 I bought myself Salifert test kits for nitrate and phosphate. My tap water tested ~1ppm for NO3 and I got no blue colour at all with the PO4 test which according to the manufacturers means less than 0.03 ppm (<0.03 ppm).  My tank was 2.5-5 ppm for NO3 and <0.03 ppm for PO4. I tried the tests on my unheated goldfish tank in the front room and got 25-50 ppm  NO3 and 1 ppm for PO4 so I think the kits were working. The levels I found in the cyano tank were low from what I had read, even reef keepers might have been happy with them. It seemed that, if excess nutrients had been the cause of my cyano outbreak, then I had removed the cause. But the cyano persisted, in fact it thrived. I decided that since I was doing water changes like I was overstocked, I may as well be overstocked, so I put in five cardinal Tetra and hit the internet, big time.

The strategy that caught my eye was all about controlling algae and cyano in planted freshwater tanks by phosphate limitation. The idea was that if you stimulated plant growth enough by supplying nitrate and potassium (K) and CO2, but no phosphate, then the plants and algae would use up all the phosphate and the cyano would die. There was no way I was getting into CO2, not in a low light tank, so I started adding K2SO4 so as to achieve 15 ppm K (the four mineral water companys around me all say their bottled water contains 1-2 ppm K) and trace elements. I also monitored NO3 levels. These remained at 2.5-5 ppm for the first five weeks, but then dropped so I started dosing KNO3 to keep levels in a similar range. Eight weeks of nutrient dosing, water changing and gravel vacuuming followed, the cardinals grew strong and wiley. It was during this period that I replaced my arch-like tank ornament with a piece of bogwood. I had read that the tannins from bogwood reduced pH. Some claim cyano prefer alkaline conditions which may be relevant as the pH of my water is 7.6-8.0. I had also read that tannins were toxic to cyano. Here is a still from a video shot on Sunday 3rd April 2011 (week 37).

The plants have grown nicely but the thing that makes me think the nutrients made a difference is that the Ellodea have changed, they have broader and longer leaves than previously. Unfortunately the cyano was also doing well. Not exactly the behaviour of an organism that was starved of its food supply. Note the lilaeopsis has gone, plants on the bottom are difficult to clean and tend to die. I have no memory of the small broad leaved plant I've planted in its place.

This is the day after a water change. I siphoned a load of cyano off the Ellodea but didn't have time to do the bogwood before my 20 liter bucket filled up. The bogwood had no effect on the cyano I could see, if anything it seemed to grow more lushly on the bogwood. Maybe my piece of bogwood was so old that it had leached all its tannins out. It didn't seem to discolour the water but I was doing frequent water changes. The gravel surface looks OK, the cyano on it may have grown back overnight, but notice the filth below. Looking back now I can see that my hours of gravel vacuuming had not prevented the build up of mulm, otherwise know as fish s**t. But who cares? There should be some mulm in the gravel, it's part of the Nitrogen cycle. It gets broken down by bacteria into ammonia and NO3 which can be taken up by plants. Setting up a fish tank is like establishing an ecosystem and it seemed to me that some decaying matter was to be expected. So why was my ecosystem increasingly dominated by cyano? Confused, I once again suckled from the teat of the internet. In desperation I decided it was time to seek medical help.

Chapter III. Cyanobacteria control by increasing circulation

Whenever evil befalls us, we ought to ask ourselves, after the first suffering, how we can turn it into good. So shall we take occasion, from one bitter root, to raise perhaps many flowers. 

Leigh Hunt (1784 - 1859) 

So many people have problems with cyano over the years, and have asked for advice on fish forums, that the forums have generally amalgamated the discussions into FAQs or sticky's. While writing this blog I once again searched for such advice and the front page of google returned me to the same FAQs that I had read back in Jan 2011. I think it would be fair to say that the main causes of cyano problems are generally listed as.

• excess nutrients (nitrate (NO3) and phosphate (PO4) mainly) due to insufficient water changes, poor tank hygiene, overfeeding and/or overstocking.
• excess light/direct sunlight (although some claim insufficient light/wrong spectrum of light).
• insufficient circulation, cyano is said to favor stagnant conditions or even oxygen depletion.

You'll notice that the first point is the same as the suggested cause of green water which was easily solved by increasing the frequency of water changes. I guessed overstocking could have been an issue as at the time I had 21 fish. But according to aqadvisor.com, with the small species I had, 21 fish = 92% stocking. The tank didn't look overstocked to me. As for overfeeding, I have yet to see a piece of food make it to the bottom of the tank uneaten, so it's not that there was food rotting on the substrate. I never fed more than was eaten in two minutes but it was something to bear in mind.  

As for light, as I said before, I was pretty sure my set up was 'low light' due to the plants I was able to grow. But I did notice that the tank gets 1-2 hours of direct sunlight/day. I set the timer so the lights turned off for two hours in the middle of the day, which I remember reading on a forum had cured someones cyano problem. So the tank was getting 10 hrs artificial light and whatever the pale Scottish Sun could provide. Insufficient light didn't seem likely as I had enough light for plants to grow. Poor spectrum also seemed dubious as at the time the bulb I was using was only five months old. It also struck me that the most enthusiastic proponents of the idea that the deterioration of spectra from aging light-bulbs cause algal problems were light-bulb manufacturers. 

Circulation, this really caught my imagination. I had under-gravel filtration at the time, powered by a rising column of bubbles from an air-stone, but flow rates were probably low and as far as I knew there might have been 'dead spots' in the tank. I decided to increase water changes and increase circulation. I went back to weekly changes and in week 26 installed a power-head. The power-head made a big difference to the tank, all the plants were swaying and the fish started having to swim harder, in fact the X-rays started what looked to me like spawning.  I also became an expert at removing cyano. The best way I found was to siphon it off with the water. I attached a toothbrush to the end of my siphoning tube and found I could very efficiently remove it from the tank walls etc. and even Ellodea strands but not so well from the Amazon Swords or Java Moss.  I was still vacuuming the gravel weekly. The following photo is a still from a video taken 25-1-11 week 27.

This was shot two days after a 20 liter (37%) water change. I can clearly see the cyano growing up those Ellodea strands and the moss balls are tufty as they've been siphoned. I see I've planted Lilaeopsis in the foreground because the Java Moss had to go out, riddled with cyano it was. I then really upped the water changes. I was alternating 10-20 liter water changes every two to three days but the cyano just kept coming back. Not only that, it kept coming back more aggressively each time.  It would appear in new places and then once it had, removing it just made it come back quicker. By week 30 it became clear that increasing tank circulation had not had the desired effect. Looking back now it makes sense. It hadn't first appeared in a corner or under a rock but mid water. Why would circulation have been the cause?  It grew nicely on the power-head exhaust nozzle which must be the most circulated part of the tank. Something else was the cause and I decided to use science as my weapon. 

Chapter II. The seeds of despair

If you search the internet for tips to help getting rid of a green water algal bloom you will find the advice is to increase the frequency of water changes and improve general tank cleanliness. The idea is that a surplus of nutrients (nitrates and phosphates mainly) are responsible. So I started changing 10 liters every week and continued vacuuming the gravel. By week 14 the green water had gone so I started doing two-weekly changes with weekly gravel vacuuming. My thinking was that three weekly had been insufficient but surely twice weekly would be enough to keep the water quality up. On the 19th  December 2010 (week 22) I took a video of the tank, from that I captured this still.

Looking at it now, it's obviously cyanobacteria growing on the Ellodea. It's not green! At the time I thought it was hair algae. I watched with pleasure as the cyano got established and by week 24 I introduced three Ottocinclus algae eaters. I honestly thought when I released them that they would dive straight into eating the 'hair algae' as I had read on the forums about Ottos clearing a tank of hair algae in a few days. The Ottos wouldn't go near the stuff. Confused I searched the internet and found a few sites that listed all the types of algae commonly found in freshwater tanks with descriptions and photos. It was on one of these sites that I made the fateful discovery, I had blue/green algae aka cyanobacteria. A quick read up about cyano proved troubling. It seemed nothing ate it, and it was notoriously difficult to get rid of. First things first, what to do about the Ottos. It should have been no problem, people feed them all sorts of vegetables. I tried blanched and fresh cucumber, turnip, sweet potato. Nothing seemed to interest them, even the algae on the back wall of the tank that I never cleaned. They hung from the tank walls mainly, sometimes they looked like they were feeding but it wasn't the continuous browsing I had been led to expect. On Monday 17th Jan 2011 (week 25) all three Ottos were found dead. The problem with Ottos is that they can't be bread in captivity. Wild caught fish are always likely to be problematic because they have to withstand being caught and transported. I have read that Ottos are quite sensitive and difficult to keep but I'll never know if the problem was the Ottos or my tank water. Anyway, after a respectful period of mourning it was time to read up about getting rid of cyano, and embark upon a journey to the gates of Hades itself.

Chapter I. Start up and first signs of trouble

The story begins on Saturday the 17th of July 2010. My plan was simple, grow plants in the tank, keep various small species of Tetra and then maybe some Ottocinclus if I could get enough algae to grow.

I had read up about cycling the tank so I installed the under-gravel filter system (I was a fan at the time), filled it with ~54 liters of tap water and some tap water conditioner, put some plants in and left it for a week. Then in went 10 Glowlight Tetra. Next morning nine had made it (even though I acclimatized them slowly to the tank water) and were milling about. I was adding a product called "filter start " which is supposed to encourage the establishment of a population of the good bacteria that remove ammonia and nitrites (nitrifying bacteria). Even so it took four weeks until my nitrite levels dropped to zero. As far as I can make out this is about what you'd expect naturally. Nitrite levels peaked at 0.5 mg L.

During this time the Amazon Swords and Ellodea were growing nicely, but the Cabomba just sat and this red leaved plant I can't remember the name of died quickly. I was using a 24W CFL light rated at 6700K for 12 hours a day and the tank's in a well lit room with skylights. But it seems I had a 'low light' tank as (according to the forums) Cabomba requires more light than Ellodea and red leaved plants are 'high light'. The Ellodea would grow 2-3" in a week so it seemed to me there were plenty of nutrients and the water must be healthy. I decided to grow Ellodea and Java Moss and other low light plants.

In week five I added five Black Phantom Tetra and eight X-ray Tetra. I was doing 10 liter (18%) water changes every three weeks and vacuuming the gravel every week with an Algarde aquarium cleaner. It works by connecting it to an air pump. The rising column of bubbles provides suction, drawing waste up the tube and into the collecting bag. I was impressed by the Algarde, it  was powerful and easy to use and the little bag would get clogged with fish s**t (fs) so it was definitely working. However by week nine the water went green, you couldn't see through the tank lengthways it was so bad, something had to be done.

See that green/blue stuff all over everything?

Introduction

If you have been searching for solutions to cyanobacteria problems in your aquarium then this blog is for you.  I have been trying to get rid of it for two years, and I finally think I might be getting somewhere, but I've had false dawns before so I'm not celebrating yet.
If you search the internet with "blue green algae problem" or "control cyanobacteria freshwater aquarium" you will find 100s of posts on tropical fish forums where hacked off aquarists ask for help to cure their blighted tanks. I honestly think I've read all of them. I think there is some sound advice given to people with cyano problems, but there are also some dubious suggestions. Sometimes these suggestions are apparently based on science. But I think the science is being misrepresented, which upsets me, so I want to give my view on that. I've also noticed some manufacturers making cyano related claims about products which are in my view unjustified. I've tried some of the methods of treating cyanobacteria that I've found by searching the internet and I'm going to take you through them in the form of a retrospective blog. You can then decide if it's worth giving them a try in your tank. This is my direct experience and should be accurate as I have written everything I've ever done to my aquarium down

Inception

It's time to tell my story, in my own words.  It will be of interest to few but it might change your fish-keeping life.