Hello,

I have been thinking about the current understanding of why BGA/cyanobacteria occurs and what to do about it. The current methods are to dose more nitrate, 3 day blackout, lots of water changes, cleaning, and/or medicate the tank to kill it, etc. It seems that often though, these methods are met with only limited success, and to be honest a blackout or medication of the tank to kill it seems extreme to me.

I have a hypothesis as to a possible cause. It is that a slightly anaerobic substrate might be the main or possibly only cause. Now I will explain why I am thinking this so I can get all of your input or correction.

It has been established that BGA can thrive in a low nitrate environment because it has the ability to use atmospheric nitrogen as nitrogen source, and the rest of algae and plants can't do that.

That always seemed off to me initially, because that (in my mind at the time), would only explain BGA growing at the water surface, not down in the water. I looked into it further and found that using atmospheric nitrogen doesn't mean that it needs nitrogen from the air, but more specifically that it can use N2, which is the form of nitrogen found in the atmosphere. N2 is also dissolved (in varied amounts) in aquarium water at all times, and that to me was a key to the puzzle.

What caught my eye a few days ago when I was reading about anaerobic substrates and anaerobic bacteria, was that the bacteria that live in anaerobic substrates actually use nitrate as their food source and give off N2 into the water as their byproduct.

You can have low (or no) measurable levels of nitrate in the aquarium water and still have varying levels of nitrate in the substrate.

If BGA doesn't particularly care about nitrate dosing you would think it shouldn't increase its' growth when nitrate is dosed, but when I tried just dosing extra nitrate to my tank to get the BGA to go away, it actually got worse. What if that increase in BGA growth had nothing to do with the nitrate itself and everything to do with the added nitrate then feeding a slightly anaerobic substrate bacteria more of what it wanted and then having more N2 put out into the water as a byproduct? The aquarium water N2 level might actually be what causes the BGA to begin/increase.

I was thinking about this, because if I dosed the extra nitrate right after a good gravel and tank cleaning (a cleaning of all possible anaerobic zones in the substrate) the BGA didn't really respond to the nitrate addition at all (or at least it was heavily delayed by at least a few days), but if I didn't do that cleaning first it would sometimes double or triple in mass within 24 hours. Could that be the true key to the cause of BGA and its' eradication, making sure the substrate stays as aerobic as possible to keep dissolved N2 as low as possible in the water? Now I give it to you all for your thoughts and experiences to see if they fit or refute my hypothesis.

This hypothesis would also explain how it is said that BGA thrives in poor circulation, but that people (of which I am one) can actually have a small BGA outbreak spot in an area of the tank that has great circulation and well aerated water. It is not the specific spot that is the key, it is the fact that somewhere in the tank anaerobic bacteria is adding extra N2 to the water and that is feeding it no matter where it is located.

As I have said before, I am just trying to figure this stuff out, and I don't know too much about it all yet, so if I am making a wrong assumption in anything I have said let me know. If anyone else has already mentioned this I apologize. I have not read or found anything like this online in my searches so far, but I could have easily missed it.

Have a good one, Jeremy

I hope you'll bump this thread when Tom gets back. I can't answer your question, but thought that I would give some input.

A quote from Tom on BGA prevention:


I think the key word here is prevention. Once the BGA is established, it is a tough customer. It seems that established BGA does not respond to NO3 additions, as you have also noticed. Your theory may be correct, because Tom's conditions of prevention above may very well eliminate anaerobic areas in the tank, thereby eliminating anaerobic bacteria. If your theory is right, I'm certain that good CO2 would help prevent BGA, since the plants will pearl more and help reduce anaerobic areas. Dusko's "Basic Algae" article lists excess organic loading as a possible cause for BGA, so good tank maintenance also removes that as a cause.

I just started some non-CO2 tanks. Typically, a non-CO2 tank would not have 10-30ppm NO3, and also you do not do water changes. Hey, wait a minute -- a non-CO2 tank is not fulfilling a very high percentage of Tom's no-BGA conditions! So now I'm thinking that I had better make doubly sure to prune old leaves and clean the filter and tank well. I get a little lazy about that with my EI tank and have gotten away with it. It's good to get this reminder.

Jeremy,
Your theory does fit perfectly what I experienced.

My initial foray into planted tanks started with a 10g that developed major, major bga issues. It didn't seem to matter what I did - it came back every time and choked off my plants, even though the portions of plant that didn't get covered by bga seemed to be growing well. Incidentally, I had about 2" or maybe sometimes 3" of gravel, really quite a lot for that sized tank. I would gravel vac it, but the bga just kept coming back. Finally I just removed my lighting and waited for my plants to die and gave up. To my surprise, my java ferns took off. I guess they were happy that they weren't being choked by bga anymore. With the insanely low lighting, bga couldn't really grow. I turned my lights back up (to 1.5 wpg) but bga just kept coming once again. Just coincidentally, I decided to change out my substrate, with no thought to how it would affect the bga. I replaced it with a much shallower layer of gravel. Within a week, the bga was gone and never came back. The only places I get bga now are on filter outflows where they are very close to the lighting, also exposed to the atmosphere to some degree like on a hob, and it never spreads.

Hi,

Interesting article, I have same experiences.

My second BGA infestation within 4 months I just killed with anibiotics. CO2 was low for a few days because the bottle ran out and the days before taht I introduced my bought fish to the tank and introduced fish feeding). My tank (500 liters / 130 US gallons) was running on a small eheim (2216) with a fluidized sand bed filter, very good water flows and a lots of plant growth. GBA was spreading like crazy at that moment, and turning on CO2 wasn't helping anymore and almost every plant was covered in it. Water changes of 50% in 4 days wasn't helping and I didn't want to turn out the light (150 watts of T5) for a few days.

In holland it's common to have GBA in small highlighted, aerated spots with low lovel of NO3. But GBA on the gravel and deep levels in the tank are more likely caused by bad nitrification, lots of organic polution (overfeeding), GBA close to unaerated parts of the tank. Well, thats what experts say over here. Startup of tanks with not the right conditions like mine weren't helping preventing an outbreak.

The last to weeks I introduced a second Eheim (2218) and better filter medium cleanup, Excell like (EasyCarbo) and antibiotics and now hope that mecanic filtration and restoring nitrification processes will prevent another one.

how did you obtain the antibiotics?

groetjes,

yme

You can use erythromycine 600 mg/300l or 80 usG. once. If needed , dose again after 1 week. I once had bga , after this therapy they never came back. Where you get the antibiotics? I got it from the hospital where i work.

gr guy

I brought this exact subject up 2005 at APD:
[APD] Re: BGA, N2 gas and heterocyst

It was a big no from Tom Barr since the fresh water Cyanobacteria that we have in our tanks don't have heterocysts and thereby can't fix N2.

I don't think I got an answer on the question I asked in the above message.

It seems fresh water Cyanobacteria can form very tight colonies and inside create an anearobic environment where they actually CAN fix N2 without heterocysts.

And if so, N2 supplement from an anearobic substrate or the air would give our cyanobacteria a nice lead nitrogen wise =)

But BGA, at least the species we see, are far far far from being the least bit NO3/NH4 limited in any way.

So there's no need nor advantage in fixing N2 gas.

I think that's the bigger relevant issue here so we ought to look elsewhere.
Low NO3 seems to induce spores to grow faster, but it it does in no way imply that the BGA is Nitrogen limited.

Big difference.

I know of no algae that's limited in our aquariums vs the typical potential limiting levels in natural FW systems.

The planted tanks we have are very rich for all algae.
Limitation is not a factor.

Inducement/germination of spores are.

Regards,
Tom Barr

Good. That is what I'm telling folks in Sweden.

This leads me to a simplification I've thought out.

Let's say jumpin oxygen levels and/or jumping NH4-levels is what makes algae really go nuts (start growing).

To me it seems like you can see what kind of algae that will start growing by looking back how you have run your aquarium before the O2-dip/NH4-spike:

*) Unstable CO2-levels - BBA
*) Low NO3-levels and/or high PO4-levels - Cyanobacteria
*) High NO3-levels - Dust algae
*) Low PO4-levels, very good climate overall - Green spot algae
*) High Fe-levels - Hair algae (Cladophora, Pithophora, Spirogyra, Audouinella?)
*) High Urea-levels - Staghorn or Green water

Yes, it seems to becoming more clear what induces algae, rather than treating algae like plants that are only growing vegetatively.

The idea about inducement is key.
You also need a control and tank with good optimal conditions prior to the manipulation.

The experimental treatment/manipulation needs to be done on purpose so you know what to look for and what to expect. Otherwise you have a much more difficult time analyzing anything and might wait years for any observations.

I'm not so sure there inducement in a single factor either.
While I've mentioned it many times, I also hold out for a potential other causes, --after all..........there might be more than one cause and there might be several things in conjunction that cause algae to bloom/germinate.

This is reasonable.

Adding more light or less can certainly influence results.
Measuring light and CO2 are difficult. These both play a huge role, far more than all the BS garbage about nutrients............

Yet few aquarist even really critically measure CO2 and even fewer measure light.

So why the focus on nutrients?
I guess it's because the test kits are 5-10$ and the light meters and CO2 meters are very costly.

Yet plants and algae are not one dimensional, they grow due to light, CO2 and nutrients, not just one issue.

So in order to get around such issues, we have to pick a CO2 level, keep it there etc, same for light and know what they are so we can compare to other systems.

Only then can we really build a model that's fairly predictive to what we see in aquariums. We can pick aquariums that are low light, say 100 micmols or less down to 25, 100-250, 250-500 etc. These likely will need to be matched with CO2.
Say stable non CO2 for the lower light, and stable CO2 for the low light as well.
Then a bit higher for the next step and so on............
Now you can start fiddling with nutrients.

Still, for whatever light and CO2 level you chose, each thing must be non limiting.
This rules out confounding issues. Otherwise you have to start all over because you cannot tell what is causing what.

I see all sorts of post about nutrients and few, if any, address such basic issues.
It's sad really.

Because there's very little actually getting done there and the myths just keep coming.

I fight against it and folks poo poo on you

But.........wind bags aside, there are many more that do read the post and understand that what I'm arguing does make sense and has some logic.
That's why, as well as my own personal curiosity, I keep after this stuff.

Regards,
Tom Barr