Columnaris (Flavobacterium columnare) is one of the most aggressive freshwater fish diseases - the disease can kill multiple fish within 48 hours of visible symptoms. Treatment protocol: Move infected fish to a hospital tank with mature filtration. Dose Kanaplex per manufacturer instructions for 7-10 days. Daily 25% water changes with parameter-matched water + dechlorinator. Re-dose Kanaplex after each water change. Alternative for milder cases: Furan-2 5-7 day course. Prevention: Avoid stress (overcrowding, sudden parameter changes, aggressive tankmates). Quarantine new fish 14-21 days. Visual signs: White or grey saddle-shaped patches on the back, mouth fungus appearance, frayed fins. Often confused with fungus but spreads faster. See the full columnaris guide for symptoms checklist + alternative treatments.
The full Q&A library answers the most-searched aquarium questions. Browse calculators and disease database for related help.
Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.
Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.
Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.
Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.
Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.
How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.
What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.
How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.
Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.
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