Fish diseases

Discrete white spots of about 1 mm, like grains of salt or semolina, scattered over the body and fins. Fish rub against decor, clamp their fins and later gasp — the parasite hits the gills hardest, so a fish can be suffocating while only a few spots show on the skin.

A yellowish-rust film like gold dust over the skin, gills and fins — much finer than white grains. It shows best in the dark under a flashlight held at an angle. Fish rub against objects, clamp their fins and start labouring for breath early, because the parasite attacks the gills first.

Flat, pale patches, often with a yellowish or tan tinge, where the skin loses its shine — around the mouth, along the back (the classic saddle-shaped band at the dorsal fin), on fin edges and gills. A cottony growth can form around the mouth. It spreads fast — sometimes within a day or two.

A grey-white tuft like cotton wool rising off the body surface — usually in one place, on a wound, a knocked-off slime layer or dead tissue. It grows and spreads over days. The photo shows a trout with two classic cotton tufts.

A swollen belly, but the scales lie FLAT and the fish stays active and keeps begging for food. Most often after generous feeding with dry food. Females in breeding season fill out naturally — symmetrically, with no other signs.

A swollen body with scales standing out — seen from above, the fish looks like a pinecone. Bulging eyes sometimes join it, and the fish turns listless and stops eating. The photo shows a goldfish with its scales lifted off the body.

A slow disease unfolding over weeks and months: the fish wastes away despite eating, the back hollows, the belly may swell on an already thin fish, non-healing ulcers appear, paleness, sometimes a bent spine. Fins can crumble too — older literature calls it “false fin rot.”

Fin edges crumble, split and recede, often with a whitish, dark or reddened rim along the eroding line. It starts at the edge and creeps toward the fin base over weeks. The photo shows a betta with a tail beginning to fray, the affected area circled.