Fish Disease

Thick pale mucus sloughing away in patches with laboured breathing, classically in newly imported clownfish — Brooklynella, often called clownfish disease.

Fins held tight against the body, reduced activity or hiding — a general stress signal.

One or both eyes appear hazy or white — can indicate infection, poor water quality or injury.

Swollen abdomen or scales standing out (pinecone appearance) — may indicate dropsy or organ failure; act quickly.

Fins appear shredded, milky at the edges or shortening over time — bacterial infection often follows injury or stress.

Identify common fish disease symptoms — ich, fin rot, dropsy, velvet, marine ich and more — with causes, treatment steps, and prevention.

Fish dart and scrape their flanks against substrate or décor, often with rapid gill movement — irritation, commonly from gill flukes or early parasites.

Fish repeatedly gulp air at the surface — usually low dissolved oxygen or gill irritation.

Small pitted craters in the flesh above or behind the eye, often in cichlids and discus — hole-in-the-head, linked to Hexamita and long-term stress.

Clustered white or grey nodules on fins or body resembling a cauliflower floret — typically lymphocystis, a slow viral condition.

Fine white spots on a marine fish, often with flashing and rapid breathing — likely Cryptocaryon, which is more aggressive than freshwater ich.

One or both eyes protrude from the socket — fluid behind the eye, usually from injury or infection rather than a disease in its own right.

Fine blood-red streaks through the fins or reddened patches on the body — often septicaemia, a bacterial infection in the bloodstream. Treat as urgent.

The fish cannot hold its position — floating tail-up, sinking to the bottom or rolling over. A buoyancy problem, not necessarily an infection.

A reddened open wound with a pale eroded rim and missing scales — an ulcerative bacterial infection that needs prompt attention.

Fine gold or rust-coloured dust on the body — may indicate Velvet (Oodinium), visible under side light.

Progressive weight loss with a sunken belly and visible spine despite the fish eating — chronic wasting, which has several possible causes.

Cotton-like white growth on mouth, fins or body — often fungal or columnaris infection.

The \"Big Three\" marine parasites: A guide to Marine Ich, Velvet, and Brooklynella. Master quarantine protocols and the 76-day fallow period for reef safety.

Beyond White Spot: Identifying and treating Velvet, Flukes, and Internal Parasites. Learn the flashlight test for Velvet and the effectiveness of Praziquantel.

Biosecurity and prevention: Strengthening your aquarium's first line of defense. Learn how environmental stability and stress management prevent 90% of diseases.

Setting up a safety net: The ultimate guide to aquarium quarantine protocols. Learn how to manage a bare-bottom QT tank and the essential 4-week observation period.

The Ich nemesis: A master guide to White Spot Disease. Understanding the three-stage parasite life cycle and mastering heat, salt, and medical treatment options.

Cotton Wool Disease: Mastering fungal infection diagnosis and treatment. Learn to distinguish true Saprolegnia fungus from deceptive bacterial \"mouth rot\".

Identifying and treating bacterial infections: A detailed guide to Fin Rot, Dropsy, and Pop-Eye. Learn the critical difference between Gram-positive and Gram-negative treatments.

Managing viral diseases in aquariums: Understanding Lymphocystis, DGIV, and Neon Tetra Disease. Learn why immunity and nutrition are the only defenses against viruses.