# Cyanobacteria



## JeffK (5 May 2021)

Hi guys,

I'm having trouble with cyanobacteria. I wasn't sure where to post it, but I figured it would be best to post it here.

It's quite a mystery, actually. I have three tanks at home. Two Akvastabil Fusion 100 and one Akvastabil Fusion 130. They are all lighted with two Fluval Aquasky 2.0 LED's (all on the same settings) and filtered with Cristalprofi filters. They are all tinted, as in blackwater tanks. Lots of leaves, lots of wood, not a lot of plants. Except for the two smaller tanks, they're full with floating plants (Pistia). I put the same food in all the tanks, mainly frozen brine shrimp (rinsed in tap water), but I also feed some veggy flakes in the bigger tank, because the fish in there need it in their diet. I routinely add new water to these tanks every week, 100% RO water.

Now, one of the smaller tanks has been developing some small spots with cyanobacteria. I also had a cyanobacteria problem in a previous tank (ugh, the stench was horrible), so it might've stuck on some plants and came into the new tank. The smaller tank had a HUGE phosphate problem, which is one of the reasons I bought a new, bigger tank. I figured that somehow, the same problem had occured in the new tank, as the cyanobacteria came back, but I just tested the water and there's almost no phosphate detectable in the water. Same as in the other, same sized tank. Both tank's no3 were also practically zero. I'm at wits' end at how the bacteria has continued to develop and is slowly spreading around the tank.

Does anyone of you have any clue, why one of two almost identical tanks has developed this issue? 

The only one I could think of was perhaps a lack of flow or oxygen, so I turned up the water flow. I hope it helps, but I have my doubts. I'd love to hear your ideas.

Thanks guys,
Jeffrey


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## ceg4048 (5 May 2021)

Hello,
        BGA is caused by low nitrate in the tank. Another cause is dirty filters. Clean you filters and/or add KNO3.

Cheers,


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## glasscanvasart (5 May 2021)

@ceg4048 I‘ve also associated Cyanobacteria with detritus and decaying plant material when my Monte Carlo was melting in adaptation. I also noticed that lower Nitrogen levels might be a cause, as it was never a problem until I tried the same thing, but with different substrate. Though this wasn’t consistent with when I poured a bunch of KNO3 into the bowl (in excess of 100ppm) and the Cyanobacteria came back with a vengeance.

More circulation is likely to help and H2O2 at 3% kills Cyanobacteria as does Erythromycin, but I‘m not sure this is legal or practical.


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## ceg4048 (5 May 2021)

glasscanvasart said:


> @ceg4048 I‘ve also associated Cyanobacteria with detritus and decaying plant material when my Monte Carlo was melting in adaptation. I also noticed that lower Nitrogen levels might be a cause, as it was never a problem until I tried the same thing, but with different substrate. Though this wasn’t consistent with when I poured a bunch of KNO3 into the bowl (in excess of 100ppm) and the Cyanobacteria came back with a vengeance.
> 
> More circulation is likely to help and H2O2 at 3% kills Cyanobacteria as does Erythromycin, but I‘m not sure this is legal or practical.


Hi,
   Yes, Erythromycin is very effective, however it's use is typically frowned upon. Really it's unnecessary as all it takes is to keep the tank clean with regular water changes and to consistently dose the tank with KNO3. 
Nitrate,  Erythromycin  and peroxide all damage BGA, but that's not the point. The salient feature of KNO3 is that it feeds the plants with the most useful form of Nitrogen, which keeps them healthy and allows them to resist a BGA attacks. 
So there is no point in applying a toxic solution if the root cause (malnutrition) is not addressed, otherwise it will simply return another day.

Cheers,


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## JeffK (6 May 2021)

Yes, I've read about adding KNO3 to battle cyanobacteria, but wouldn't that be the case if there was any PO4 to begin with?

Also, the filter is clear, the water is clear. Yes, there is detritus, but there's probably more in the other tanks and they have no problems at all.

I'd rather understand why it's developing in this tank and not in the other tanks, before putting stuff in, which I don't like in general.


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## PARAGUAY (6 May 2021)

Assuming ruling out @ceg4048 whats been saidas a cause do any of the tanks get sunlight catching the substrate?


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## castle (6 May 2021)

I suspect you introduced BGA from your previous tank, I don't think you can get rid of BGA without killing all life in the tank,  _I may be a little extreme there_.

I get BGA in combination where flow is low and sunlight is hitting the tank. I'm not sure what causes it.

I've learnt a lot from BGA:

It's mobile, almost certainly in the water column at all times.
High flow means it cannot settle (easily).
It's weak; if I add some (already aclimatised) Pothos to the aqurium BGA growth slows.
It's weak, if I remove an area of substrate and replace with "old, wet" sand (from another still running aquarium) BGA growth slows.
It's weak, syphon it away, wave your fingers about, 80% water changes every other day.  (or remove all fish into some buckets with tank water, then do a couple of full drains).
BGA also will grown near decomposing matter, I recently saw in a tank a alder male catkins, which had broken down, but BGA certainly had found.

Basically, I think BGA can multiply when there is something limiting everything else, or something rich that nothing else can conquer first. I'm less inclined to say this is element based, but perhaps this is from a low amount of beneficial bacteria in the substrate/filter? Either way, if it's in the tank you're probabaly never going to be fully rid, but I wouldn't worry, good housekeeping and it is very manageable.


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## JeffK (6 May 2021)

PARAGUAY said:


> Assuming ruling out @ceg4048 whats been saidas a cause do any of the tanks get sunlight catching the substrate?


Some, but not a lot. The other tanks get some sunlight aswell. It really brings out the colour in fish. You should watch an Alestopetersius nigropterus in direct sunlight. They're beautiful.



castle said:


> I suspect you introduced BGA from your previous tank, I don't think you can get rid of BGA without killing all life in the tank,  _I may be a little extreme there_.
> 
> I get BGA in combination where flow is low and sunlight is hitting the tank. I'm not sure what causes it.
> 
> ...


Yeah, I guess I just have to deal with it. It's not spread out too much so far. A bit of the substrate, one Anubias leaf and a few floating plants so far. It seems like it likes to grow close to the light. Atleast, in the previous tank, it only grew on Anubias leaves close to the surface or on floating plants. I never 

I've darkened the water, so I can remove the floaters without spooking the fish too much. If this doesn't work, I guess I'll have to do as @ceg4048 said and at a bit of KNO3 to see what it does.


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## ceg4048 (7 May 2021)

JeffK said:


> Yes, I've read about adding KNO3 to battle cyanobacteria, but wouldn't that be the case if there was any PO4 to begin with?


Hi, sorry, I'm not sure why you referenced PO4, which has nothing to do with the fact that having you plants suffer NO3 starvation is a typical cause of BGA.


JeffK said:


> Also, the filter is clear, the water is clear. Yes, there is detritus, but there's probably more in the other tanks and they have no problems at all.


As I mentioned, it's not about the tank per se, but about how the plants are responding. There are insufficient details to do a comparison of what's happening in each tank. When you have an algae problem in a planted tank it's because the plants are dying , usually due to malnutrition. If you are not feeding the plants regularly, and if the water you are using does not already have nutrients in it from it's source, then the plants are not able to withstand the attacks and problems such as this tend to occur. Plants require regular feeding of NO3, PO4 and K. In a CO2 tank the gas application needs to be done well. In non-CO2 tanks one has to be careful regarding the lighting intensity. You mentioned in your original post that NO3 was zero. This is never something to be proud of in a planted tank so I'd probably look to address this issue first, which is easy using KNO3. I'd also suggest adding KH2PO4 as well as it's possible that once you fix the NO3 deficiency the PO4 may then become the limiting factor and you may then see the development of PO4 deficiency symptoms.

Cheers,


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## JeffK (7 May 2021)

Thank you for your help. I'll try and start adding nutrients to see if it helps.


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## tam (7 May 2021)

I find addressing the under lying issue (and there maybe more than one factor that triggers it) and then blacking out gets rid of it most reliably. So, I would manually remove any you can (tooth brush and syphon), doing a water change at the same time. Address any excess mulm, clogged filter, etc. and make sure your circulation is good. Then switch off the lights and cover the glass for five days. There should be none visible when you uncover. Do another water change and keep on top of any issues e.g. make sure you are water changing, dosing plants etc. and you should hopefully have resolved it.


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