Loading...
Loading...
Symptoms, common causes and what to check — for the most common aquarium issues.
43 results
A parasitic copepod (not a true worm) that embeds in fish skin, causing visible red lesions and secondary infections. Common in ponds. Treatment: manual removal + dimilin.
A stubborn, dark algae that grows in tufts on plants, decorations, and equipment. Often indicates fluctuating CO₂ levels. Removed by spot-treating with hydrogen peroxide.
A bacterial infection (Flavobacterium columnare) causing white/gray patches on the mouth, fins, or body. Can progress rapidly and become fatal without treatment.
A type of brown algae that forms snot-like patches with air bubbles. Difficult to eradicate and can be toxic to corals. Treatment: UV sterilizer, dosing, manual removal.
A parasitic crustacean that attaches to fish, causing visible disc-shaped parasites, scratching, and blood spots. Common in ponds. Treatment: manual removal + potassium permanganate.
Parasitic flatworms (Dactylogyrus or Gyrodactylus) that attach to gills and skin, causing rapid breathing, flashing, and white mucus. Highly contagious. Treatment: praziquantel.
A disease causing pits and holes on the head and lateral line, common in cichlids. Associated with poor water quality, stress, and Hexamita parasites.
Small, tentacled freshwater polyps that can sting and kill tiny shrimp fry. They multiply rapidly through budding and are often introduced on plants or live food.
The most common fish disease — caused by Ichthyophthirius multifiliis, appearing as small white spots like salt grains. Highly contagious but treatable with temperature increase and medication.
Small flatworm pests that multiply rapidly in aquariums. Harmless to adult fish but can attack shrimp fry and compete for food. Often a sign of overfeeding.
A condition where one or both eyes protrude abnormally, usually caused by bacterial infection, poor water quality, or physical injury. Treatment: antibiotics and clean water.
A fungal-like infection causing white, cottony patches on fish. Usually secondary to injury, stress, or poor water quality. Treatment: antifungal medication and improved conditions.
A condition causing fish to float uncontrollably, sink to the bottom, or swim sideways. Common in fancy goldfish and bettas. Can be caused by overfeeding, constipation, or infection.
A parasitic disease caused by Oodinium that produces a fine, gold or rust-colored dusting on the fish body. Highly contagious and often fatal if untreated promptly.
Fins look frayed, ragged or are visibly shrinking with white or red edges.
Water quality slowly worsens over months or years despite regular small water changes.
Long green strands coat plants, hardscape and glass. Common in young or bright tanks.
Grey-green branching tufts shaped like antlers on plant tips and filter outlets.
Leaves yellow, develop pinholes or new growth looks twisted and stunted.
Abdomen swells and scales stand out like a pinecone — usually a bacterial infection.
Sudden temperature swings after water changes, heater failure or power cuts stress fish.
The biological filter fails after aggressive cleaning, media replacement or a long outage.
Pest anemone infestation in reef tanks
A dusty brown coating on glass, plants and decor, common in new tanks.
Common LPS coral disease causing tissue loss
Milky or hazy water that never fully clears.
Stress response causing coral to expel zooxanthellae
Slimy blue-green or dark purple patches with a foul odor.
Fish hover at the surface, breathing rapidly. A possible oxygen emergency.
Fish hide constantly, refuse food and fade in color.
Water turns bright green from suspended single-celled algae.
Heater failure causing temperature drop
Heater malfunction causing overheating
Elevated ammonia levels cause burns, redness and rapid breathing.
Algae driver and long-term fish health concern
Toxic nitrogen cycle intermediate harmful to fish
The filter output weakens, reducing circulation and filtration.
Rapid dangerous drop in aquarium pH
Gradual pH change over time
Leaves turn transparent, mushy and fall apart shortly after planting.
Fast-progressing coral tissue death, typically SPS
Gradual coral tissue recession
Tiny white salt-like grains on the body and fins of fish.