Cyanobacteria - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 10-29-2010, 10:52 PM Thread Starter
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A couple weeks ago I diagnosed my 20g tank with cyanobacteria. I have cut back my light by 3 hours a day (for a total of 8 hours instead of 11) and I have been doing two 25% water changes a week. Will this cure the problem before it begins to kill my plants and maybe fish? If not, what else should I do?
Also... How do I prevent this in the future? Right now I only have fairly hardy fish in the tank, but I am planning on putting in Bolivian Rams soon, so any advice is welcome. I really don't want to lose any fish.

I'll post a picture of what I thought was algae, but turns out to be cyanobacteria. I wish I caught it sooner, but I just thought it was algae.
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post #2 of 4 Old 10-29-2010, 11:20 PM
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My gravel gets like that too! I have been gravel vaccing it up every week during water change and things have been fine if unsightly. I've got Bolivian rams too. Is this an issue I should be worried about? It's been like this for at least a month and doesn't seem to be hurting anything.

30g SE Asian Tank
15 Lambchop Rasbora
2 Gold White Cloud Minnows
3 Dwarf Chain Loaches
2 Powder Blue Dwarf Gourami

55g Amazon Tank
2 Wild Type Angels
1 Marble Angel
1 Black Angel
1 Koi Angel
2 Bolivian Rams
14 Pristella Tetra
10 Dwarf Pencilfish
2-3 Twig Catfish (to come)
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post #3 of 4 Old 10-31-2010, 05:39 PM
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The following may help you [it is not mine, it was written by Dusko Bojic for another site]. As always, be very careful if you decide on using antibiotics. I have never resorted to this; some plants will be harmed and even killed with erythromycin (pygmy chain swords come to mind). The cause is organic--regular large water changes help. RTeducing light even to a blackout is sometimes suggested, but this can also harm the plants. And any method that does kill cyanobacteria will result in a lack of oxygen (due to the decomposing mass) and high ammonia/nitrate.

Blue-Green Algae
even though it's commonly called blue-green algae (BGA), it's not classified anymore as one. This "algae" is actually cyanobacteria, a form of life that has both animal and plant characteristics. It forms slimy, blue-green, sheets that will cover everything in a short time and give off a strong, characteristic scent. If left to over-run the tank, cyanobacteria may kill plants and even fish. It doesn't stick and can be easily removed manually, but will return quickly if the underlying water quality issue is not fixed. It can be treated with Erythromycin and other antibiotics, but this method should be done carefully since it might affect the nitrifying bacteria in the gravel and filter, and improper use of antibiotics always brings the risk of developing a more resistant strain. When the BGA gets killed by the algaecide it will start to rot and through that process it will reduce Oxygen levels in the tank. Since the nitrifying bacteria needs O2 to transfer ammonia/nitrites into nitrates the nitrifying process will slow down. If algaecide is used, make sure to test the ammonia/nitrite levels. Remove all the visible algae to prevent it from rotting in side the tank.

Some aquarists use the black-out method previously described, where black bags are wrapped around the tank for 4 days and held in complete darkness. It is advisable to raise NO3 levels to 10-20 ppm before starting the black-out period. Manually remove as much BGA as you can before the blackout, and dead matter after the blackout.Egeria densa (Elodea) and Ceratophyllum demersum are good plants to have in a tank, since these plants are known to secrete natural antibiotic substances that can help prevent BGA. Establishing lots of healthy, fast-growing plants from the day you start the tank, dosing the nitrate levels to maintain 10-20 ppm, and vacuuming the gravel to keep the tank free of decaying matter is the best way to prevent this "algae". BGA can be found in aquariums with very low nitrates because it can fix atmospheric nitrogen. BGA seems not to like high CO2 levels and stronger water currents.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #4 of 4 Old 10-31-2010, 08:46 PM
i used to have a lot of that stuff, i had to dose with maracin for about a week to kill it all. Now it only shows up when i slack on my water changes. I had to cut my tank light time back to limit its growth. Its one of those things that once u get, it will never truely go away unless you really nuke your tank, which i didnt want to do because i didnt want to risk my fish.

I noticed that overdosing excel also works, but thats also risky to do since it could hurt your fish if the CO2 levels rise too much.
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