# How to combat out-of-control cyanobacteria?



## PaulLamb (Nov 15, 2009)

I am having trouble once again with my 10-gallon planted live-bearer aquarium. This time cyanobacteria are growing out of control - smothering the plants, "de-beautifying" the aquarium, and generally smelling bad (smells like putrid grass cuttings). I believe I inadvertently introduced the stuff into the aquarium along with a beautiful feathery native plant I brought home from the local lake (I actually "caught" the plant on my fishing line, and was surprised that something so nice grows locally). The cyanobacteria problem began a couple of weeks after adding this plant to the aquarium.

This is the same aquarium that had problems in the past with unicellular "pea soup" algae blooms as well as out-of-control beard algae, which I eventually resorted to eliminating with oxythylene / dimethyliminio ethylene chemical treatments (these problems have not returned). This cyanobacteria, however, does not seem to respond to these chemicals (probably since it is technically a bacteria, not an algae). My only option has been bi-weekly cleanings (tediously scrubbing each plant leaf) along with partial water changes and frequent filter-pad replacements. A recent 2-week vacation away from home resulted in the blue-green slime completely taking over (the fish seem to enjoy swimming through the slimy folds and crevices, but my wife wasn't too happy with the foul odor permeating through the house when we opened the front door).

Searching google, I've found that this stuff generally attacks aquariums that have poor water quality, and the past out-of-control algae bloom problems would seem to support that analysis. However, the aquarium has been established for some time, has plenty of plants, and is only stocked with 4 of my nicest male swordtails and 2 oticincli. Additionally, I've been doing frequent partial water changes and gravel cleanings (at least weekly). The fish themselves show no signs of stress, and the swordtails are quite vigorous and vibrantly colored. The other plants are growing fine as well (so long as I keep cleaning the scum from their leaves).

My latest attempt has been a complete scrub-down of the aquarium (everything except the bio-filter), and I increased the temperature slightly, lowered the PH a bit, and added a pinch of salt (hopefully this will make conditions less desirable while not harming the fish or plants). It is too early to tell if this will have any effect, but I'm rather doubtful as this stuff has been quite prolific. I've read that erythromycin phosphate is an effective treatment, but that would wipe out the biological filter as well. I may ultimately have to resort to that, but I thought I would post here before reaching for the chemicals.

Anyone know of other safer treatments besides erythromycin for eliminating cyanobacteria while not harming the bio-filter? Are there varieties of fish/invertibrates that really enjoy chowing down on the stuff? The oticincli don't seem to care for it... can't blame them - I wouldn't eat anything that foul-smelling either.


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## JimW/Oscar (Jul 4, 2010)

Cyanobacteria is gram negative while most bacteria believed to be the useful nitrifiers in our aquariums are aerobic and gram positive. If you could find treatments containing Kanamycin like API's Triple Sulfa which would be effective mostly against the cyanobacteria while not measurably harming your biological filter. Maracyn II's active ingredient is Minocycline which is derived from tetracycline, while Mardel claims Maracyn II is for the treatment of gram negative bacteria it unfortunately can also damage your biological filter.


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## Corwin (May 23, 2010)

Also reduce lighting and increase water changes

if your over feeding that could be an issue as well


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## emc7 (Jul 23, 2005)

I've heard the opposite, that it thrives in "too clean" tanks that don't feed normal algae and plants enough to compete and that you should add more fish. I think the seeds may be in the water supply, as I went from none, to several tanks nearly overnight. It is growing in soft-water tanks, as well as hard, alkaline, cichlid tanks. But the worst one is the jewel cichlid tank with alkaline, soft water. It smothers hornwort and pearlweed. It does seem to need some light, I don't have any in the dark, brown-algae tanks. But a single bulb ans a little sunlight is enough to make it go nuts.


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## TheOldSalt (Jan 28, 2005)

This particular cyano has been a major pain in waters across america for the past few years now, and it's only getting worse. Sorry about it getting into your tank. 
I'm afraid that, being a bacteria, everything you've done so far to eliminate it has been undone by your filter, which you did not clean. You have been re-seeding the tank after each cleanup by reinstalling your infected filter.

I guess you know what that means.
Go ahead and nuke the filter as well with the next tank cleansing, and quickly re-establish it with a product like Seachem's Stability, which works wonders.

Good old erythromycin gets rid of most cyanos with ease, and it really is a good way to go considering the problems you've been having with this stuff. You'll just have to make a few more water changes than expected, and then you'll have to fix the filter. Better than an entire takedown & scrubbing, though. Marginally.


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## JimW/Oscar (Jul 4, 2010)

TheOldSalt said:


> I guess you know what that means.
> Go ahead and nuke the filter as well with the next tank cleansing, and quickly re-establish it with a product like Seachem's Stability, which works wonders. Good old erythromycin gets rid of most cyanos with ease.



I wonder if he could have quarantined the native plant in an anti-biotic treatment before introducing it into his tank and avoided this?

I would agree with the use of Stability and using Prime as the tap water treatment if not already doing so, but I'd disagree with the use of erythromycin, though it might kill cyanobacteria it is much more effective on Gram positive bacteria while even a tetracycline based treatment like Mardel's Maracyn II or Tri-Sulfa will be more effective against Gram negative cyanobacteria if you're going to have to accept your biological filter as a necessary loss.

I have to admit I don't know a lot about aquarium plants though, perhaps tetracycline would be more damaging to them than erythromycin?


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## PaulLamb (Nov 15, 2009)

emc7 said:


> I've heard the opposite, that it thrives in "too clean" tanks that don't feed normal algae and plants enough to compete


I suppose I probably made the problem worse with the algae treatments, basically eliminating the competition.



TheOldSalt said:


> You have been re-seeding the tank after each cleanup by reinstalling your infected filter.


I figured as much. I was just hoping I could change/improve the water conditions so the stuff wouldn't grow so crazily. I wouldn't mind an occasional bit on the glass or gravel, but this out-of-control growth has been a real pain.



TheOldSalt said:


> Go ahead and nuke the filter as well with the next tank cleansing





JimW/Oscar said:


> a tetracycline based treatment like Mardel's Maracyn II or Tri-Sulfa will be more effective against Gram negative cyanobacteria if you're going to have to accept your biological filter as a necessary loss


I guess I'll have to go ahead and treat the problem chemically. I mainly don't want to loose these swordtails, so I think I'll put them back in the community swordtail aquarium until I'm sure this aquarium is stabilized.



JimW/Oscar said:


> perhaps tetracycline would be more damaging to them than erythromycin?


I definitely want to start with whatever is safest for the plants, if anyone knows from experience. I'll wipe them out as a last resort if necessary, I guess.


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