Symptoms, causes, treatments.

Pinhead-sized white spots scattered across the body, fins, and gills — like the fish has been dusted with salt. Fish flash against decor (scratch sides of body), clamp fins, breathe rapidly, and lose appetite as the parasite multiplies. Gill infestations can suffocate before spots are visible on the body.

Thin red worms (1-3 mm) protruding from the anus, often visible only intermittently as they retract. The worms anchor in the intestinal wall. Fish becomes thin despite eating, develops a bloated abdomen, loses color, and produces white stringy feces. Late-stage cases stop eating. Most common in livebearers (guppies, mollies, platies), Discus, and Apistogramma.

Pitted lesions on the head, particularly above the eyes and along the lateral line — start as small pinpricks and erode into deeper craters that may leak pale stringy mucus. White, stringy feces. Loss of appetite and weight loss despite the fish appearing to feed. Color fading. Most pronounced in Discus, Oscars, Severums, large cichlids, marine angels, and tangs.

Tiny white spots on the body and fins — slightly larger and rounder than freshwater Ich. Heavy infestations show breathing distress as gills are colonized. Flashing against rock and substrate. Discolored patches, ragged fins. Most virulent on tangs, angels, butterflies — but no marine fish is immune. Mortality is high if untreated.

Fine gold or dusty sheen across the body — like the fish has been sprinkled with powdered sugar. Often easier to see under a flashlight in a dim tank. Rapid gilling, scratching, color loss. Velvet kills FAST — fish can die within 24-48 hours of symptoms appearing, often before the gold dust is widely visible. Sudden mass mortality without obvious cause is often Velvet, especially in clownfish.

Excess mucus production — fish develops a cloudy, peeling, gray-white slime coat that sloughs off in sheets. Rapid breathing, gasping at the surface, lethargy, refusing food. Often presents first in newly-imported clownfish, especially wild-caught Maroons and Tomatoes. Mortality is high and fast — 24-48 hours from first symptoms is common.

Fin edges fray, blacken, or develop a white milky margin. Tissue progressively erodes from the tip inward, sometimes reaching the body if untreated. Affected fins look ragged or shredded. In advanced cases the fin rays show as exposed white spikes. Lethargy and loss of appetite often accompany.

White or grayish-yellow patches around the mouth, gills, or back — often resembling a fuzzy 'saddle' across the dorsal surface (giving the disease one of its names). Frayed fins, lethargy, gulping at the surface. Gill infection is the fast killer: fish can die within 24 hours with no visible body lesions. Often misdiagnosed as fungus because of the cottony appearance, but Columnaris is bacterial.

Chronic, slow progression over weeks to months. Wasting (hollow belly, spine prominently visible despite eating). Spinal curvature, fin erosion that doesn't respond to standard antibiotics. Eye protrusion or cloudiness. Skin ulcers that won't heal. Sudden death of multiple older fish in an established tank with no obvious water-quality cause is a classic Fish TB pattern.

Fish floats sideways at the surface, sinks tail-first to the bottom, swims upside down, or struggles to control depth. Often otherwise alert and trying to eat. Most common in fancy goldfish (egg-shaped bodies compress the bladder), bettas, and large gouramis.

Pitted erosion along the lateral line — the sensory canal running down each side of the fish — and on the head. Lesions start as small pits and progressively widen, sometimes reaching down to bone. The wounds themselves don't typically kill but disfigure permanently if untreated. Common in tangs, angels, large cichlids (especially in captivity-stressed individuals).

Severe abdominal swelling combined with scales protruding outward like a pinecone — the hallmark sign. Bug-eyed appearance (exophthalmos). Lethargy, loss of appetite, sometimes pale gills. The pinecone scale pattern indicates internal fluid buildup pushing scales away from the body.