Fish Disease Database
Identify, treat and prevent common aquarium fish diseases.
White Spot (Ich)
The most common aquarium parasite, appearing as grains of salt across the body and fins.
Fin Rot
A bacterial infection that frays and erodes the fins, usually triggered by poor water quality.
Velvet
A parasitic infection that coats fish in a fine gold or rust-coloured dust.
Dropsy
A symptom, not a single disease — fluid build-up causing a swollen body and raised 'pinecone' scales.
Swim Bladder Disease
A disorder of buoyancy control, common in fancy goldfish and bettas.
Popeye
Swelling behind one or both eyes causing them to bulge outward.
Columnaris
A fast-moving bacterial infection often mistaken for a fungus, forming white cottony patches.
Gill Flukes
Microscopic parasitic worms that attack the gills, causing severe breathing distress.
Anchor Worm
A visible crustacean parasite that embeds in the skin, leaving a thread-like tail.
Fungal Infection
Cotton-wool-like growth on the skin, fins or eyes, usually on already-injured tissue.
Hole in the Head
a disfiguring condition of cichlids where pits form on the head and lateral line, linked to Hexamita, poor water and diet
Hexamita
an internal parasite causing white stringy droppings and wasting, and a common trigger of Hole in the Head
Malawi Bloat
a fast, often fatal swelling condition of African cichlids, usually triggered by the wrong (too high-protein) diet
Constipation
a common digestive problem from overfeeding, causing a swollen belly and stringy faeces, easily fixed with diet
Ammonia Poisoning
a critical emergency where toxic ammonia burns the gills, usually in uncycled or overstocked tanks
Nitrite Poisoning
a deadly stage of the nitrogen cycle where nitrite stops the blood carrying oxygen, common in new tanks
New Tank Syndrome
the cluster of problems caused by adding fish to an uncycled tank, driven by ammonia and nitrite spikes
Cloudy Eye
cloudy or milky eyes, usually an early warning of poor water quality, injury or bacterial infection
Camallanus Worms
internal nematode worms that protrude as red threads from a fish's vent, common in livebearers
Internal Parasites
hidden worms and protozoa that cause slow wasting and stringy faeces despite a good appetite
Neon Tetra Disease
an incurable parasite causing fading colour, a broken stripe and a curved spine in tetras and other small fish
Fish Tuberculosis
a slow, hard-to-cure bacterial wasting disease - note it can rarely infect humans through open cuts, so wear gloves
Lymphocystis
a harmless but unsightly viral disease forming cauliflower-like lumps on fins and body, which usually self-heals
Bacterial Septicaemia
a dangerous internal bacterial infection showing as red streaks, ulcers and bloating, needing fast antibacterial treatment
Costia
a microscopic skin parasite ('slime disease') that coats fish in excess grey mucus and irritates the gills
Chilodonella
a microscopic protozoan parasite causing a cloudy slime coat and gill damage, thriving in cool dirty water
Trichodina
a skin and gill protozoan that irritates fish and causes flashing, thriving where water quality is poor
Black Spot Disease
harmless-looking black pepper-like spots from fluke larvae, usually on wild-caught fish; rarely a real threat in tanks
Gas Bubble Disease
an uncommon condition where gas-supersaturated water forms bubbles under a fish's skin and eyes
Skin Flukes
microscopic skin worms that cause flashing, excess slime and skin irritation, treated with praziquantel
Epistylis
a protozoan that forms fuzzy tufts resembling fungus or ich, thriving in dirty water
Bacterial Ulcers
open red sores from opportunistic bacteria, usually on fish weakened by poor water or injury
Fish Lice
visible disc-shaped crustacean parasites that clamp onto fish and cause intense flashing
Leeches
blood-feeding parasites usually introduced with wild-caught fish or pond plants
Marine Ich (Cryptocaryon)
the saltwater version of white spot, a marine parasite needing quarantine treatment away from corals
Marine Velvet (Amyloodinium)
an extremely fast, deadly marine parasite that coats fish in gold dust and attacks the gills
Brooklynella (Clownfish Disease)
the dreaded 'clownfish disease', a fast marine protozoan that strips slime from stressed new fish
Uronema
an aggressive marine parasite causing red sores and sudden deaths, worse in high-nutrient tanks
Egg Binding
when a female fish cannot release her eggs, causing a persistently swollen belly