What are the symptoms of Columnaris?

Greyish-white fluffy or cottony patches starting around the mouth, lips and head; A saddle-shaped pale eroded band across the back and upper flank; Fin edges turning white and dissolving, with adjacent fins fusing; Frequent gaping, refusal to feed, rapid breathing and resting on the bottom, with possible mass mortality within days. It usually starts with: Warm water combined with poor water quality, the combination the bacterium thrives in; Skin wounds from netting, fighting or transport; Overcrowding and low oxygen weakening the skin slime barrier; Large temperature swings at water changes, or the pathogen arriving with new fish.

How do you treat Columnaris?

In order: 1. Isolate every affected fish at once (Columnaris advances fast and spreads easily, so isolate on sight with dedicated tools; check the display tank for other pale patches and assume the whole tank has been exposed.) 2. Change water and clear organic debris (Change 30-50% of the water with matched temperature and siphon out leftover food and waste. Organic matter is this bacterium's breeding ground, so cutting waste matters more than adding drugs.) 3. Lower the temperature to the middle of the fish's range (Columnaris multiplies faster in warm water, so lowering the temperature slowly into the 24-26 °C range can slow the disease; drop no faster than 1 °C per hour and confirm the species tolerates it.) 4. Low-level salt bath (Bath in the hospital tank at 1-3 g of non-iodised salt per litre for 5-7 days; scaleless fish such as loaches, plecos and corydoras do not tolerate salt, so use antibiotics alone for them.) 5. Run a full course of antibiotics (Choose oxytetracycline, florfenicol or a sulfa drug at the label dose and complete a 7-10 day course in the hospital tank; do not stop as soon as symptoms fade, which invites a relapse and selects for resistant bacteria.) 6. Observe for a week for new lesions (Keep watching for a week after treatment to confirm the lesions have closed and no new saddle patches appear before returning the fish.)

What medication treats Columnaris?

Oxytetracycline: Hospital tank only, as a bath or in food at the label dose for 7-10 days. It kills nitrifying bacteria, so dosing the display tank risks an ammonia rebound; stop UV and remove carbon during treatment.; Florfenicol: Hospital tank only, mixed into food at the label dose for 5-10 days. It is a prescription-class antibacterial, so check local regulations and withdrawal periods.; Potassium permanganate: Hospital tank only, as a brief bath at the label dose, watching the fish throughout and pulling it out at once if it struggles violently. It damages plants, the biofilter and invertebrates alike.

G-04 / 07Freshwater

Columnaris棉口病

Very urgent. It progresses by the day with high mortality; once saddle lesions appear it is often too late, so act the same day.

Illustration to come

G-04 / 07 · Columnaris

SpecificationsDisease atlas

Cause: Bacteria
Severity: Severe
Contagion: Highly contagious
Corals / inverts: Not safe
Also known as: Cotton mouth disease、Saddleback

Symptoms

Greyish-white fluffy or cottony patches starting around the mouth, lips and head
A saddle-shaped pale eroded band across the back and upper flank
Fin edges turning white and dissolving, with adjacent fins fusing
Frequent gaping, refusal to feed, rapid breathing and resting on the bottom, with possible mass mortality within days

Typical triggers

— Warm water combined with poor water quality, the combination the bacterium thrives in
— Skin wounds from netting, fighting or transport
— Overcrowding and low oxygen weakening the skin slime barrier
— Large temperature swings at water changes, or the pathogen arriving with new fish

Treatment, in order

1 · IsolateIsolate every affected fish at onceColumnaris advances fast and spreads easily, so isolate on sight with dedicated tools; check the display tank for other pale patches and assume the whole tank has been exposed.
2 · Water changeChange water and clear organic debrisChange 30-50% of the water with matched temperature and siphon out leftover food and waste. Organic matter is this bacterium's breeding ground, so cutting waste matters more than adding drugs.
3 · HeatLower the temperature to the middle of the fish's rangeColumnaris multiplies faster in warm water, so lowering the temperature slowly into the 24-26 °C range can slow the disease; drop no faster than 1 °C per hour and confirm the species tolerates it.
4 · SaltLow-level salt bathBath in the hospital tank at 1-3 g of non-iodised salt per litre for 5-7 days; scaleless fish such as loaches, plecos and corydoras do not tolerate salt, so use antibiotics alone for them.
5 · MedicationRun a full course of antibioticsChoose oxytetracycline, florfenicol or a sulfa drug at the label dose and complete a 7-10 day course in the hospital tank; do not stop as soon as symptoms fade, which invites a relapse and selects for resistant bacteria.
6 · ObserveObserve for a week for new lesionsKeep watching for a week after treatment to confirm the lesions have closed and no new saddle patches appear before returning the fish.

The standard treatment uses copper or formalin, which is lethal to corals, shrimp, snails and everything on live rock. Treat in a quarantine tank only, and leave the display tank fallow for the full period above before returning the fish.

Medications and cautions

Oxytetracycline: Hospital tank only, as a bath or in food at the label dose for 7-10 days. It kills nitrifying bacteria, so dosing the display tank risks an ammonia rebound; stop UV and remove carbon during treatment.
Florfenicol: Hospital tank only, mixed into food at the label dose for 5-10 days. It is a prescription-class antibacterial, so check local regulations and withdrawal periods.
Potassium permanganate: Hospital tank only, as a brief bath at the label dose, watching the fish throughout and pulling it out at once if it struggles violently. It damages plants, the biofilter and invertebrates alike.

Prevention

Avoid keeping the temperature at the high end of the species range for long periods
Maintain water quality and oxygen, keeping stocking below what the filter can process
Quarantine new fish for 2-4 weeks and do not share equipment with established fish
Isolate injured fish promptly, since wounds are the entry point for this bacterium

Frequently asked questions

What are the symptoms of Columnaris?: Greyish-white fluffy or cottony patches starting around the mouth, lips and head; A saddle-shaped pale eroded band across the back and upper flank; Fin edges turning white and dissolving, with adjacent fins fusing; Frequent gaping, refusal to feed, rapid breathing and resting on the bottom, with possible mass mortality within days. It usually starts with: Warm water combined with poor water quality, the combination the bacterium thrives in; Skin wounds from netting, fighting or transport; Overcrowding and low oxygen weakening the skin slime barrier; Large temperature swings at water changes, or the pathogen arriving with new fish.
How do you treat Columnaris?: In order: 1. Isolate every affected fish at once (Columnaris advances fast and spreads easily, so isolate on sight with dedicated tools; check the display tank for other pale patches and assume the whole tank has been exposed.) 2. Change water and clear organic debris (Change 30-50% of the water with matched temperature and siphon out leftover food and waste. Organic matter is this bacterium's breeding ground, so cutting waste matters more than adding drugs.) 3. Lower the temperature to the middle of the fish's range (Columnaris multiplies faster in warm water, so lowering the temperature slowly into the 24-26 °C range can slow the disease; drop no faster than 1 °C per hour and confirm the species tolerates it.) 4. Low-level salt bath (Bath in the hospital tank at 1-3 g of non-iodised salt per litre for 5-7 days; scaleless fish such as loaches, plecos and corydoras do not tolerate salt, so use antibiotics alone for them.) 5. Run a full course of antibiotics (Choose oxytetracycline, florfenicol or a sulfa drug at the label dose and complete a 7-10 day course in the hospital tank; do not stop as soon as symptoms fade, which invites a relapse and selects for resistant bacteria.) 6. Observe for a week for new lesions (Keep watching for a week after treatment to confirm the lesions have closed and no new saddle patches appear before returning the fish.)
Is Columnaris contagious, and how urgent is it?: Contagion: highly contagious. Severity: severe. Cause: bacteria. Very urgent. It progresses by the day with high mortality; once saddle lesions appear it is often too late, so act the same day.
What medication treats Columnaris?: Oxytetracycline: Hospital tank only, as a bath or in food at the label dose for 7-10 days. It kills nitrifying bacteria, so dosing the display tank risks an ammonia rebound; stop UV and remove carbon during treatment.; Florfenicol: Hospital tank only, mixed into food at the label dose for 5-10 days. It is a prescription-class antibacterial, so check local regulations and withdrawal periods.; Potassium permanganate: Hospital tank only, as a brief bath at the label dose, watching the fish throughout and pulling it out at once if it struggles violently. It damages plants, the biofilter and invertebrates alike.
Is the treatment for Columnaris safe for corals and inverts?: No. The standard treatment (copper or formalin based) is lethal to corals, shrimp, snails and everything on live rock. Treat in a quarantine tank only, and leave the display tank fallow for the full period given above.