This is a very common ailment of aquarium fishes, particularly those that prefer more alkaline water with a higher pH like the livebearers (mollies, platys, swordtails, etc.). It is so common in live-bearing fishes that Columnaris is often referred to as “Livebearer's disease”. The premier signature of this malady is a rise in the skin between the gill cover and dorsal fin, coupled with a milky appearance to the scales which then quickly ulcerates. Because of this characteristic, it is also referred to as “Haystack or Saddleback disease”. Lesions start out as raised, slimy patches with a red margin that ulcerates within a few days revealing the layer of skin below the scales. Advanced ulcerations usually turn to a reddish golden color from the initial grayish white. There are quite a few of closely related bacteria that can be responsible for this disease, but the most common is Flexibacter Columnaris (also referred to as Flavobacter columnare, Flavobacterium columnare, or more generically as Myxobacteria). Tropical fish are particularly susceptible to Columnaris as the bacterium is most virulent in waters warmer than 64 degrees Fahrenheit.
Columnaris, which is a member of the Phylum Myxobacteria is a gram- negative, rod-shaped bacterium that is saprophytic (an organism that grows on and derives its nourishment from dead or decaying organic matter) and found embedded in slime (like that on a fish’s skin and gills) where it forms complex colonies. These bacteria are unique in that they have an ability to move by gliding along surfaces with no visible or known means of locomotion. All of these bacteria are virulent and cause debilitating damage. This condition is also referred to as “fin and tail rot” as it attacks the thin, sensitive tissue of the fins quite vigorously. In progressed cases, the bacteria infests the gill tissue as well which is evidenced by a slimy gray appearance instead of the vibrant pink that the gills should have. Fish affected with Columnaris often hover near the surface of the water and shimmy the tail back and forth while holding the pectoral and dorsal fins (or what's left of them) close to the body. Fins will have a milky appearance, and then just rot off, seemingly overnight, leaving only the ulcerated base. The mouth can also be affected with a yellow to brownish slimy appearance on the lips and an inability to close the mouth. Left untreated, it is fatal and can quickly spread to other fish in the aquarium. Outbreaks are usually triggered by stress-inducing conditions such as deteriorating water quality or a sudden rise in water temperature, which is one of the factors for outbreaks in outdoor ponds as spring sets in. The bacteria that attack the fish are usually part of the natural bacterial fauna in an aquarium, but they will colonize a weakened fish with as much vigor as they form on a pile of decaying fish food.
Columnaris, better known as Flavobacterium columnare (aka Flexibacter columnaris) is one of the more virulent (extremely infectious, malignant, or poisonous) bacterium that attacks fish. Once the fish become stressed and a few bacteria are able to infect the fish, it quickly pinwheels out of control as these bacteria reproduce by binary fission. This means that the simply split in two once they attain an adequate size so one turns into two, two turn into four, four turn into eight, and so on. This process only takes a few seconds and millions of them can develop overnight. Needless to say, swift action must be taken in order to reverse the condition.
The first thing you need to do is change about 25 percent of the water with a gravel siphon. Columnaris bacteria normally feed on decaying matter, like the detritus in the gravel and left over fish food. If you remove a good portion of the detritus, you will cut the bacteria’s population down considerably. Fish immunology is not a level playing field. One specimen (say a newly introduced one) may succumb to the level of bacteria in the tank, while the others may not. They simply have a higher tolerance for the level of bacteria present. Many aquarists make the mistake of assuming a newly introduced fish “brought” the disease into their tank. That isn’t quite how it works. Not really “not quite” how it works, but not even remotely. What you need to realize is that nearly all the organisms that cause disease in fish are already in the aquarium to begin with, in small numbers that a healthy fish’s immune system can handle. This isn’t to say that disease introduction doesn’t happen on occasion (as with crustacean parasites like Anchorworms and Fish Lice), but the greatest detractor to fish health is stress, pure and simple. The stress of being transported can weaken a perfectly healthy fish to the point that when it is introduced to a new environment (especially one with a higher concentration of pathogenic organisms than it was previously exposed to) it becomes a breeding ground for bacteria and protozoans. That being said, if you reduce the stress level in the tank, you can optimize your chances of affecting a successful cure.
Your next best ally in combating Columnaris (and a host of other pathogenic nasties as well) is plain aquarium salt. Salt performs several functions in turning the tide against disease outbreaks. First, it has an antiseptic (meaning it inhibits the growth and reproduction of disease-causing microorganisms) quality, and clears excessive gill and skin mucous along with small particle debris.
Second, it affects the osmotic pressure on the fish by reducing the amount of water that enters the fish’s body through osmosis (diffusion of fluid through a semi permeable membrane from a solution with a low solute concentration to a solution with a higher solute concentration until there is an equal concentration of fluid on both sides of the membrane). If you have no idea what all this has to do with Columnaris, don’t worry. Reducing the osmotic pressure on the fish is like turning the sprayer down on the garden hose when you are watering your roses. They need water, but not at such a rate that the pressure from the nozzle damages the delicate petals and leaves. Fish need to uptake oxygen and other dissolved gases in the water through the gills, but in a heightened state of stress and disease, the gills are overused and become inflamed and irritated. To further complicate matters, Columnaris often infects the gills as well once it gets a good foothold on the rest of the fish’s body. Salting the water slows the osmoregulation process down and allows the fish’s immune system to catch up to the increased presence of the disease. Single-celled organisms like Columnaris experience a change in osmotic pressure to the point that where they usually have a slow and constant ingress of water, they experience a sharp digress of water as it flows out of the cell into the water around them. Basically, adding salt dehydrates the bacteria and they die. The same would happen to the fish if you added more salt than what is required to dehydrate the bacteria. Because the fish is a larger, more complex organism, it can adjust to the change in osmotic pressure while the microscopic bacteria can not.
The third way salt aids in disease control is it has astringent qualities as well, meaning it draws together or constricts tissues to effect a stop in the loss of blood or body fluid. Drawing the damaged tissues together reduces inflammation and initiates healing, allowing the tissues to heal on their own. Once the loss of fluid is slowed and cellular debris is cleared, and the action of the pathogen is interrupted or inhibited, within hours the skin will go through a process called granulation. This entails fibroblasts (cells that give rise to connecting tissue) laying a bed of collagen (the fibrous protein of connective body tissues) and then filling defects in the tissue and forming new capillaries. Next comes contraction, where the wound edges start to pull together to reduce the defect, then epthelialization occurs. This means the wound forms a layer of epithelial cells, which are the cells that have very little intercellular substance and form the covering of most internal and external surfaces of the body and its organs. This is the last stage in wound-healing. During this process, it is imperative to encourage the natural healing process. Using a product that performs this function as well as further inhibiting bacterial action is ideal.
Aquarium Pharmaceuticals has a product called Melafix that does exactly that. Melafix features the essential oil of the Australian Tea Tree (Melaleuca alternifolia), which is distilled from the fragrant leaves. The fragrance is the first thing you will notice about Melafix. It has a clean, penetrating quality to it, but it is not irritating. The fragrance is from various terpenoid (unsaturated hydrocarbons found in essential oils and oleoresins of plants) substances that are produced by the plant and functions as a defensive chemical. These defensive chemicals protect the plant from the action of pathogenic bacteria and fungi. Tea tree oil extracts (terpene along with a few others) have been used for their therapeutic effects for hundreds of years. Not only is it highly effective against bacteria like Columnaris, it also has the same astringent and antiseptic qualities of salt and is a natural anti-inflammatory. It is safe to use with invertebrates (corals and anemones included) and will not harm the beneficial bacteria in your biological filter.
Now that your fish are on the right track to healing, you need to get them eating again. Usually the first thing they do when the fall ill is stop eating. If they aren’t eating, they aren’t ingesting any nutrients. If they aren’t ingesting proteins, fats, carbohydrates, vitamins and minerals, their ability to regenerate tissue is greatly reduced and wound-healing will be delayed unless you can stimulate the fish to eat. Kent has a product called Garlic Xtreme that works wonders on fish that refuse food. Just use one drop of it once a day on the dry or frozen food, let it absorb, and then offer it to the fish. The Garlic Xtreme can be used long after your fish have healed as a supplement to good health. There are several anti-protozoan remedies on the market now that feature garlic extract, so it also has benefits outside stimulating the appetite. It is also recommended you invest in a good quality test kit and regularly test your water. A stable environment with water low in metabolic waste products (ammonia, nitrite and nitrate) supports fish health and longevity and greatly reduces the chance you will encounter disease outbreaks in the first place.
If you suspect Columnaris is what is affecting your fish, the following steps should be taken to help the fish make a recovery:
- Give the aquarium an equipment check. Inspect the heater, air pumps, airstones, powerheads, pumps and filters to ensure they are working properly. Disease breakouts are always preempted by a bout of stress, which is almost always attributed to water quality.
- Make sure all fish are present and accounted for. Check under rocks for missing fish, since that is usually where they can be found after they expire. Remove any carcasses and discard.
- Test the water so any waste management issues can be addressed. Elevated levels of ammonia and nitrite contribute greatly to the weakening of the fish and the presence of disease.
- Change 25% of the aquarium water with a gravel siphon (even if test results don’t indicate elevated levels of ammonia or nitrite), removing as much detritus as possible, and refill with water of the same temperature and pH as what is in the aquarium. Be sure to treat tap water with the appropriate dosage of dechlorinator/water conditioner. Reducing the amount of organic waste in the tank increases the efficiency of medications, particularly organophosphate-based ones used for treating parasites. It also helps remove the egg sacs and developing cysts of parasites that have settled in the gravel.
- Increase aeration in the aquarium by adding a second air pump and a few airstones. Diseased fish have a harder time performing gas exchange in the gills (osmoregulation) and need all the help they can get.
- Remove any activated carbon or resin-based filtering products for the duration of the treatment, but keep the filter floss in place.
- Dose the aquarium water with the appropriate amount of aquarium salt that creates a tonic level. Follow the dosing directions on the package. Most will recommend a tablespoon per ten gallons, others may recommend up to 2 tablespoons per gallon. Always dissolve the salt in a container of aquarium water first and add it slowly to the aquarium. Keep in mind many catfish, silver-scaled fish, or very small fish may have an adverse reaction to the addition of aquarium salt. If you have these fishes, add half the dose one day and half the dose the next, or divide it in thirds and add it over three days.