Blue Green Algae (Cyanobacteria)

[Beardownman]

I am having problems with blue green algae. I change 25% of water each week with a vacuum to clean sand. The aquarium is about 6 months old, only had this problem for the last month. Nitrite and Amonia are both reading 0 Ph is 7 and the nitrate reads 12.5mg/l. I have added air stones and a large powerhead to aid circulation which is happening nicely (loads of tiny bubbles and swirling current) but does not seem to help, this stuff just keeps on growing! . 77 litre tank with only about 12 young guppies which I feed Very little twice daily. 2 elodea Densa and 1 African tiger lotus now getting covered in this stuff as well as the substrate. After cleaning it grows back very rapidly to cover the tank again within a week.
Any help would be greatfully received.

 

[KittyKat]

There are a number of ways to treat against cyanobacteria. The most effective way is with an anti-biotic (be careful not to use something which will kill the filter bacteria, or remove the filter for the duration of the treatment, making sure that there is no ammonia).

The other way is with a blackout: generally one which is a few days long works.. you will need to make sure to not feed the fish during this period and make sure absolutely no light gets in. Start by removing all visible algae and doing a large water change.

There are a number of different speculations as to the cause, including high phosphates, low nitrates, poor circulation. The actual cause does depend on which exact species of cyanobacteria it is. I would recommend a review of your set up and potentially changing some things.

 

[mark4785]

I'm of the opinion that cyanobacteria is near impossible to remove once it has taken hold. If a lack of nitrate causes it, then, from experience, highering the nitrate will not cause it to diminish. The only thing that is effective once it has taken hold is to do a 4-6 day blackout on the aquarium to stop it from photosynthesising.

From observation, white spores in the water (many thousands of them) settle on surfaces in the tank and eventually turn into cyanobacteria. So doing very large water changes both before and after a blackout is also a good cyanobacteria preventative as it will remove those spores.

Don't go down the route of using anti-biotics as it will kill the filter bacteria that you are in need of to neutralise ammonia and nitrite. Large amounts of cyanobacteria are better than problems created by nitrogenous build up.

 

[ian]

I don't think anyone can completely rule out the use of erythromycin for the clean up of bga. There are quite a lot of articles on the use of this method and there's a few members who have used this method. It's clear that it does work at killing the bacteria. There is also some grey area when it comes to filter bacteria, if you read the articles even in a simple google search you will find many that did stringent testing after the use of erythromycin and found no ammonia spikes or the like. Personally I would use it as a last option, but it's the option that will work.

 

[RadaR]

Don't go down the route of using anti-biotics as it will kill the filter bacteria

From what I've heard, the antibiotic commonly used (Maracyn) is gram negative and so wont kill your filter bacteria (which are gram positive).
However I agree to stay away from antibiotics

 

[Beardownman]

Thanks for your replies.
I done the nitrate test with a Tetratest kit. It stated that nitrates between 12.5 and 25mg/L are good(which mine are), but anything above 50mg/L promotes BGA growth and aquatic plants start to stagnate. This is confusing as I was thinking about raising nitrates to combat the BGA and hopefully help my plants.
I have another set up almost exactly the same with 5 Elodea Densa, 1 Tiger Lotus, 6 larger Guppies 5 Neons and 2 Bristlenose. This I have had for about 8 months. Crystal clear water NO Cyanobacteria in sight, very healthy vigorus plant growth. The only difference is the nitrate reads 100mg/L!!
Would raising the Nitates help? If so what would you recommend for this? Any liquid plant fertilzer?

 

[RadaR]

but anything above 50mg/L promotes BGA growth and aquatic plants start to stagnate.

Where did you read that? Dont believe any of that utter rubbish.
BGA thrives in areas with low nitrates because it can absorb it's nitrogen from nitrogen fixing.
Also, plants love nitrate!

Have a look at this link on how to get rid of BGA.

 

[Beardownman]

Thanks for the link.

This is what I thought. This info came from the instruction leaflet in the Tetratest No3.
It states Above 50mg/L The growth of aquatic plants begins to stagnate, increase in algae problems (Blue Green Algae starts to grow).
Above 100mg/L plant growth will stagnate, increased problems with unsightly algae growth(strong growth of Blue Green Algae).
Maybe thats why the kit was reduced from £12.29 to £3.99!!
No wonder I get confused! You would think that Tetra would get this info right.

 

[RadaR]

No wonder I get confused! You would think that Tetra would get this info right.

I'm not suprised really. Many top manufacturers still believe in 50+years of mis-associated, wrong info. Many are still nutrient haters.

The thing is, you could easily disprove what your leaflet has said. Say you had a nice, healthy growing planted tank and then you added a known concentration of 100ppm potassium nitrate. I garuntee you wouldn't see any algae but you would see great plant growth.