Fish Health Notes

journal

From the tanks to the source, we write down what we observe and what we verify.

journal

Our latest news, aquarium notes and sourcing stories.

Aquarium Fish Disease Guide – Find Causes and Care Articles by Symptom
What should you do if your fish is gasping at the surface, has white spots or white fuzz, a swollen belly, keeps flashing, is losing weight or has cloudy eyes? Find aquarium fish disease articles by symptom, check water quality first, then learn about diagnosis and care.
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What to Do When Your Fish Is Sick – Reading Aquarium Fish Symptoms and What to Do First
What should you do if your fish won't eat, is gasping at the surface, has white spots or white fuzz, or is floating belly-up? Narrow down the cause from water quality, recent changes and symptoms, and learn when to see a vet and how to submit sick fish and water samples.
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Ammonia and Nitrite Poisoning – Fish Gasping at the Surface and How to Read Water Test Kits
Fish suddenly gasping at the surface, refusing food or spinning may be linked to ammonia, nitrite and new tank syndrome. Learn about test kit units, how pH and water temperature matter, and principles for handling it safely.
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How to Quarantine New Fish – Isolating for at Least 30 Days and Acclimating Fish to the Tank
How long should new fish be quarantined? Learn the basis for a quarantine of at least 30 days, how to prepare a quarantine tank, the ammonia risk in shipping bags, daily observation and when fish are ready to join the main tank, to lower the risk of new fish bringing disease into your main tank.
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White Spot Disease (Ich) in Freshwater Fish – The Ichthyophthirius Life Cycle and Why It Keeps Coming Back
How do you tell what white spots on a freshwater fish are? Learn about the three-stage life cycle of Ichthyophthirius, why treatment still needs to be completed after the spots disappear, and the limits of raising the temperature, cleaning the tank and quarantine.
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Velvet Disease in Freshwater Fish – Gold-Dust Symptoms and How It Differs from Ich
Gold or rust-colored dust on your fish: is it velvet? Learn about freshwater Piscinoodinium, its symptoms and gill infections, how it differs from ich, and when to see a vet.
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Columnaris Disease Symptoms – Recognizing Rotting Gills and Fins and Cottony Growth on the Mouth
A rotting tail, damaged gills or cottony growth on the mouth may be columnaris. Learn how bacterial lesions differ from water mold, the environmental triggers, why microscopy and culture are needed, and when to see a vet.
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Is White Fuzz on Your Fish Water Mold? – Wound Infections and Why Fish Eggs Grow Fuzz
How can you tell what white fuzz on a fish or its eggs is? Learn why water mold often colonizes wounds, how it differs from columnaris, and the order in which to find the underlying problem, maintain the environment and seek veterinary care.
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Causes of Dropsy and Raised Scales in Fish – How to Assess a Swollen Belly and Pinecone Scales
Is a swollen belly with scales sticking out like a pinecone a sign of dropsy? Learn to tell fluid buildup from egg retention and internal disease, how water temperature relates to infection, and when to see a vet and submit samples.
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Parasites Visible on Your Fish – Identifying Anchor Worms and Fish Lice and Understanding Their Life Cycles
Thin threads or moving discs on a fish may be anchor worms or fish lice. Learn what these two parasites look like, how their life cycles work, the damage they cause, and why pulling off only the adults can lead to repeat infestations.
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What Causes Hole-in-the-Head Disease – The Evidence on Activated Carbon, Flagellates and Nutrition
When discus, angelfish or marine fish develop holes in the head, are flagellates always to blame? We compare the activated carbon, nutrition and infection hypotheses, and lay out the limits of the research on freshwater HITH and marine HLLE.
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Goldfish Floating Upside Down or Head-Down – Causes of Buoyancy Disorders and When to See a Vet
A goldfish that flips belly-up, floats at the surface or sinks to the bottom may have a problem with its swim bladder, kidneys, a mass or its gut. Learn the difference between a buoyancy disorder and loss of balance, what the evidence says about feeding peas, and when to see a vet.
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Monogenean Parasites of the Gills and Skin – Why Fish Breathe Fast and Flash
Is your fish breathing fast, flashing or clamping its fins, but there are no white spots? Learn about monogenean parasites of the gills and skin (commonly called gill flukes): signs, life cycle, microscopy and why rechecks matter.
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White Stringy Poop and Ongoing Weight Loss in Fish – Sorting Out Internal Parasites and Feeding Problems
Is white, stringy poop, a sunken belly or a fish that eats but keeps getting thinner a sign of internal parasites? Work through what the fish actually eats, body condition, water quality and microscopy to narrow down possible causes, and learn what red worms protruding from the vent mean and what to know when submitting samples.
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Flashing, Clamped Fins and Excess Slime in Fish – Telling Skin Parasites from Water Quality Irritation
What should you do if a fish keeps flashing, clamps its fins or produces more slime? Use timing, water quality and microscopy to separate environmental irritation from skin parasites, and get to know Trichodina, Chilodonella and Ichthyobodo (costia).
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Red Patches, Bleeding and Ulcers on Fish – Telling Injury from Bacterial Infection
Red patches, bleeding or a growing wound on a fish: is it an injury or a bacterial infection? Learn how ulcers are differentiated, the role of environmental and parasitic factors, and the limits of bacterial culture and antibiotics.
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Journal

Aquarium Fish Disease Guide – Find Causes and Care Articles by Symptom

What to Do When Your Fish Is Sick – Reading Aquarium Fish Symptoms and What to Do First

Ammonia and Nitrite Poisoning – Fish Gasping at the Surface and How to Read Water Test Kits

How to Quarantine New Fish – Isolating for at Least 30 Days and Acclimating Fish to the Tank

White Spot Disease (Ich) in Freshwater Fish – The Ichthyophthirius Life Cycle and Why It Keeps Coming Back

Velvet Disease in Freshwater Fish – Gold-Dust Symptoms and How It Differs from Ich

Columnaris Disease Symptoms – Recognizing Rotting Gills and Fins and Cottony Growth on the Mouth

Is White Fuzz on Your Fish Water Mold? – Wound Infections and Why Fish Eggs Grow Fuzz

Causes of Dropsy and Raised Scales in Fish – How to Assess a Swollen Belly and Pinecone Scales

Parasites Visible on Your Fish – Identifying Anchor Worms and Fish Lice and Understanding Their Life Cycles

What Causes Hole-in-the-Head Disease – The Evidence on Activated Carbon, Flagellates and Nutrition

Goldfish Floating Upside Down or Head-Down – Causes of Buoyancy Disorders and When to See a Vet

Monogenean Parasites of the Gills and Skin – Why Fish Breathe Fast and Flash

White Stringy Poop and Ongoing Weight Loss in Fish – Sorting Out Internal Parasites and Feeding Problems

Flashing, Clamped Fins and Excess Slime in Fish – Telling Skin Parasites from Water Quality Irritation

Red Patches, Bleeding and Ulcers on Fish – Telling Injury from Bacterial Infection