Flavobacterium columnare (Cotton Wool Disease)


Tito, originally uploaded by guerogrande.

Q: AS wrote,

Hey. I have been in a dilemma over this problem for a whole week. My Betta fish lives in a rather big fish bowl with plastic plant. Recently, the tips of his fins have begun turning white and has two strands of whitish substance stuck to the fins. It started probably a week ago. My tank is of a nice temperature of 28 to 29 degrees and i add vitamins and necessary aquarium fish minerals. I feed the fish thrice a day, one pellet each. I have added fungal medicine for fin rot, cotton wool disease just two days ago but I don’t see any improvement in him. He still eats like a pig, but he is a little lethargic and does not blow bubble nests anymore. I bought the fish two weeks ago at a trade fair and changes his water every three days. HELP!

A: Hi, thanks for writing in. Often when we see white stringy strands on Betta fins we can surmise that a bacterial infection has taken hold. We often assume the infection is caused by Flavobacterium columnare (Cotton Wool Disease), a gram negative bacterium that in appearance looks like a fungus. Without basic laboratory equipment we can not be completely sure if this is the diagnosis but it is a fair educated guess to go on. The common symptoms of a Flavobacterium columnare infection are stringy or fuzzy patches on the body or fins, usually white, gray or beige in color. It is common for infected fish to become lethargic, suffer appetite loss, dull in coloration, and stop blowing bubble nests. If left untreated, the bacteria often spreads and may eventually lead to death.

The cause of these infections is usually poor water quality and without fixing the source of the problem fish tend to suffer from reoccurring illnesses. So the two major steps in treating any fish illness is to first determine and correct the cause and then treat the disease. Fish are most susceptible to disease within the first two weeks in a new environment. Since your fish became ill about a week after bringing him home, it’s fair to assume the change in environment is to blame and not necessarily the way you care for your Betta. Even if the new tank is clean and stable, the water parameters (ph, temperature, ammonia, nitrite, nitrate, gh and kh) may be different from what they were at the store. These changes can stress the fish leading to various diseases of which Flavobacterium columnare is one of the most common. Another observation I made based on your email is the water temperature. 28C – 29C [82F - 84F] is a little on the warm side and perfect for these bacteria. Flavobacterium columnare can present itself in a variety of water conditions but outbreaks tend to occur most often in the spring and summer as temperatures rise. Lowering the heat to a stable temperature between 24C – 26C [76F - 79F] may help and is still warm enough for your Betta. I also strongly encourage you to test your water regularly using inexpensive test kits sold at any aquarium store. Remember, the water parameters that effect fish are completely invisible and have no smell or color. Even if your water appears crystal clear, the tests will show you what you can’t see on your own.

So that’s how you can fix the source of the problem. To treat Flavobacterium columnare you will need a wide spectrum antibiotic that specifically targets gram-negative bacteria. If the infection is severe or spreading, treating with a combination of gram-negative and gram-positive antibiotics can help stave off both the initial and secondary infections. I like to use a combination of Mardel’s Maracyn and Maracyn-Two. Depending on the country you live in you’ll need to find a similar medication designed to treat this illness. When you begin a course of antibiotics be sure to follow the dosing carefully and finish the entire recommended course. It may take several days before symptoms subside and a second full course of antibiotics may be necessary. Be sure to remove any chemical filtration like activated carbon before treatment if you have a filter running in your bowl.

Click for more information on treating Flavobacterium columnare.

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Christie F is a Betta splendens hobbyist that enjoys spending time caring for her fish and helping new betta keepers learn the ropes. More posts by:

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