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Need to vent--- I have cyanobacteria >:(

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Feel free to weigh in with your advice and experiences.

I've had issues with this tank for a while; had to go away for 2 weeks, came back to an "infestation". I've been doing daily water changes, removed as much decor as I could. The plants are struggling. It's so frustrating. I feel bad for my betta.

Been reading up on it; I think I'm doing everything I can.

This video has been helpful, too.



Edited by BeetleLann
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On 3/1/2022 at 1:26 PM, Zenzo said:

The easiest way to get rid of cyanobacteria is to use a product like Maracyn or Erythromycin. It usually will clear up in a few days. You can also manually remove the larger sheets. 

Here is the link to Maracyn: https://www.aquariumcoop.com/products/mardel-maracyn?_pos=1&_psq=marac&_ss=e&_v=1.0

Awesome, thank you. I really need Aquarium Co-op to ship to Canada! 🇨🇦

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I agree with @Zenzo that using an antibiotic can be effective against blue-green algae (BGA / cyanobacteria) however it doesn't really address the cause of the BGA.  When it does show up in one of my tanks I first check my maintenance, have I cleaned my filters lately including re-charging my Purigen, have I siphoned off detritus accumulation, have I been over-feeding?  Next I check my water parameters including pH, hardness, and especially my nitrate ppm level. 

If everything appears good fine, if not I correct any deficiencies.  Then I physically remove as much BGA as possible by siphoning off my substrate and physically removing as much from leaves and hardscape.  After that I pick up a bottle or two of 3% hydrogen peroxide (H2O2) at the drug store (about $2 per quart) and a 10 ml oral syringe (about $3).  Then I compute the maximum amount of H2O2 I want to dose per 24 hours which is 1.5 ml per gallon (15 ml per 10 gallons).

I turn on my tank light and let it run at least two hours so the plants (and more importantly the BGA) is at full photosynthesis.  Then I turn off my filters, airstones, etc and wait 10 minutes for the water to become completely calm with no currents.  I fill up my oral syringe and find the area with the highest amount of BGA remaining.  Then I slowly 'paint' the area with the H2O2 in my syringe.  After a few minutes the BGA algae will start to bubble/fizz, that is the oxidation process killing the BGA.  After I have 'painted' as much BGA as the maximum amount of H2O2 I computed will allow I wait about 20 minutes for the bubbles to subside. After that I turn on my filters, airstones, etc and wait until tomorrow.

What is happening when I see the fizzing is the Chlorophyll portion of the BGA (the green part) is effectively bleached / oxidized by H2O2 while the bacteria portion is being killed by the antiseptic properties of the H2O2.  In other words H2O2 kills both characteristics of BGA.  H2O2 breaks down into H2O (water) and O2 (oxygen gas) during the process of killing the BGA so it is non-toxic as the 1.5 ml per gallon dosage.  I have used it with Cardinal Tetras, Rainbowfish, Apistogramms, Discus, Corydoras, livebearers, at the 1.5 ml per gallon dosage with no ill effects to the fish.  Can I dose more?  Remember that H2O2 is a strong oxidizing agent that attacks organics, which includes fish and especially their gills.  I don't want to injure my fish when treating the BGA so I keep the dosage level low.

When a BGA starts in my tank I try to catch it early, check my parameters, and dose the H2O2.  The longer I wait the bigger the problem.  It seems to show up most when I have let my nitrate levels drop, or have been lazy and not cleaned my filter as soon as I should, or if I let the plants grow too thick and reduce the water circulation in my tanks.  I typically have filtration in my tanks at a gph / gallons per hour of 10X the tank volume and clean my filters every six weeks.  The filters contain just sponges, bio-media (like bio-balls or Biohome), and Seachem Purigen to keep dissolved organics low.  -Roy 

My 45 gallon grow out tank w/ Nymphoides hydrophylla plantlets.  This tank had a small BGA outbreak about 4 weeks ago.


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