Fish Health & Disease | FreshwaterNest

Ammonia poisoning burns fish gills and is the most common cause of death in new tanks. It is invisible but fast.

Black beard algae (BBA) is the tough, dark brush that grips wood and plant edges. It signals an imbalance but is beatabl

Brown algae (diatoms) is the dusty brown film common in new tanks. It is harmless and usually disappears on its own.

Camallanus worms are internal nematodes that show up as tiny red threads protruding from a fish's vent. They are most co

Popeye is a swollen, bulging eye; cloudy eye is a hazy film over it. Both usually point to poor water or infection. Impr

Columnaris is a common bacterial infection that looks like white or grey cotton around the mouth and fins. It spreads fa

Constipated fish look bloated, sit listless, and may string white feces. It is common and usually easy to fix with diet.

Dropsy is not a disease but a symptom — fluid buildup that pushes scales outward like a pinecone. It usually signals adv

Fin rot shows as frayed, melting, or discoloured fins. It is usually bacterial and rooted in poor water. Fix the water f

Fungus appears as white, cottony growths on skin, fins, or eggs. It usually follows injury or another illness, not healt

Gill flukes (Dactylogyrus) and skin flukes (Gyrodactylus) are tiny flatworm parasites that latch onto fish gills and ski

Green water turns the tank into pea soup from free-floating algae. It looks alarming but is usually easy to clear.

Hole-in-the-head disease, also called HLLE, shows as small pits or stringy white faeces in fish like discus, angelfish a

Ich looks like salt grains sprinkled on the fish. Raise the temperature, treat the whole tank with salt or medication, a

Lymphocystis is a viral infection that produces whitish, cauliflower-like lumps on a fish's skin or fins. It looks frigh

New tank syndrome is the spike of toxic ammonia and nitrite that hits before bacteria establish. Understanding it preven

'Red pest' is the old name for bacterial haemorrhagic septicemia — a systemic bacterial infection where fish develop red

Swim bladder disorder makes fish lose buoyancy — floating nose-up, sinking, or listing. It is a symptom with several cau

Velvet is a parasitic disease that coats fish in a fine golden or rusty dust. It progresses fast, so early recognition s

Fish at the surface are usually low on oxygen or reacting to poor water. Check oxygen, ammonia and nitrite first, then t

A fish that stops eating is sending a signal. The cause ranges from harmless stress to serious disease, so read the cont