Health guide, not a diagnosis · Serious

Columnaris

Also called cotton wool disease, mouth fungus, saddleback

Signs

White or grey patches on mouth, back or gills
Frayed fins
Fast progression

Cause

Bacteria (Flavobacterium columnare), often in warm water with poor quality. Common in livebearers.

What to do

Lower temperature slightly, improve water and treat with an antibacterial medicine. Act fast.

If a fish is badly ill, talk to an aquatic vet.

Prevention

Good water quality; avoid overcrowding.

Medicines used for it

Always read the label first

Antibacterial treatmentsAntibacterial

Aquarium saltSalt & water care

Species often affected

90 species

Neon tetraParacheirodon innesi

Easy2.5 cm21–25 °C

Cardinal tetraParacheirodon axelrodi

Moderate3 cm23–29 °C

Black neon tetraHyphessobrycon herbertaxelrodi

Easy3.2 cm20–28 °C

Black skirt tetraGymnocorymbus ternetzi

Easy7.5 cm20–26 °C

Serpae tetraMegalamphodus eques

Easy4 cm22–27 °C

X-ray tetraPristella maxillaris

Easy4.5 cm24–28 °C

Lemon tetraHyphessobrycon pulchripinnis

Easy3.8 cm22–28 °C

Congo tetraPhenacogrammus interruptus

Moderate8 cm23–28 °C

Glowlight tetraHemigrammus erythrozonus

Easy4 cm24–28 °C

Rummy-nose tetraPetitella rhodostoma

Moderate5 cm24–27 °C

Ember tetraHyphessobrycon amandae

Easy2 cm24–28 °C

Bloodfin tetraAphyocharax anisitsi

Easy5.5 cm18–28 °C

Emperor tetraNematobrycon palmeri

Easy4.2 cm23–27 °C

Penguin tetraThayeria boehlkei

Easy6 cm22–28 °C

Head and tail light tetraHolopristis ocellifera

Easy4.5 cm24–28 °C

Bleeding heart tetraMegalamphodus erythrostigma

Moderate6.1 cm22–28 °C

GuppyPoecilia reticulata

Easy6 cm22–28 °C

Endler's livebearerPoecilia wingei

Easy2 cm24–28 °C

PlatyXiphophorus maculatus

Easy6 cm20–26 °C

Variatus platyXiphophorus variatus

Easy7 cm20–26 °C

SwordtailXiphophorus hellerii

Moderate14 cm22–28 °C

MollyPoecilia sphenops

Easy8 cm24–28 °C

Green neon tetraParacheirodon simulans

Moderate2.5 cm24–27 °C

Buenos Aires tetraPsalidodon anisitsi

Easy13.2 cm18–28 °C

Silver dollarMetynnis hypsauchen

Hard18 cm24–28 °C

Spotted silver dollarMetynnis lippincottianus

Hard16.4 cm23–27 °C

Red hook silver dollarMyloplus rubripinnis

Hard41.5 cm23–27 °C

Diamond tetraMakunaima pittieri

Easy6 cm24–28 °C

Black phantom tetraMegalamphodus megalopterus

Easy3.6 cm20–28 °C

Red phantom tetraMegalamphodus sweglesi

Easy3.5 cm22–27 °C

Ornate tetraMegalamphodus bentosi

Moderate4.5 cm23–28 °C

Flame tetraHyphessobrycon flammeus

Moderate2.6 cm20–26 °C

Silvertip tetraHasemania nana

Easy5 cm23–28 °C

Colombian tetraHyphessobrycon columbianus

Easy6.5 cm22–27 °C

Dawn tetraHyphessobrycon eos

Easy4.2 cm

Red-eye tetraBario sanctaefilomenae

Easy7 cm22–26 °C

Gold tetraHemigrammus rodwayi

Easy5.5 cm24–28 °C

Blue tetraBoehlkea fredcochui

Moderate5.4 cm22–26 °C

Rainbow tetraNematobrycon lacortei

Easy3.6 cm22–28 °C

False rummynose tetraPetitella georgiae

Easy5 cm22–26 °C

Brilliant rummynose tetraPetitella bleheri

Easy5 cm23–26 °C

Flag tetraHyphessobrycon heterorhabdus

Easy3.6 cm20–26 °C

Mexican tetraAstyanax jordani

Easy12 cm20–25 °C

Yellow tetraHyphessobrycon bifasciatus

Easy4.7 cm20–25 °C

Blackline penguin tetraThayeria obliqua

Easy8 cm22–28 °C

Silver tetraCtenobrycon spilurus

Easy8 cm23–27 °C

Glass bloodfin tetraPrionobrama filigera

Easy6 cm23–27 °C

Sailfin tetraCrenuchus spilurus

Moderate7 cm24–28 °C

Yellow-tailed Congo tetraAlestopetersius caudalis

Moderate6.2 cm22–26 °C

Red-eyed tetraArnoldichthys spilopterus

Easy10 cm24–27 °C

Long-finned African tetraBryconalestes longipinnis

Moderate16.4 cm22–26 °C

Ansorge's neolebiasNeolebias ansorgii

Hard3.5 cm24–28 °C

One-striped African characinNannaethiops unitaeniatus

Moderate6.5 cm22–26 °C

Three-lined pencilfishNannostomus trifasciatus

Easy3.6 cm24–28 °C

Dwarf pencilfishNannostomus marginatus

Moderate3.5 cm23–28 °C

Coral red pencilfishNannostomus mortenthaleri

Moderate3 cm24–28 °C

One-lined pencilfishNannostomus unifasciatus

Easy4 cm24–28 °C

Splashing tetraCopella arnoldi

Moderate5.5 cm24–28 °C

Red-spotted copeinaCopeina guttata

Moderate7.6 cm23–28 °C

Silver hatchetfishGasteropelecus sternicla

Easy6.5 cm24–28 °C