Marine velvet is the deadliest common saltwater fish disease. Caused by the dinoflagellate parasite Amyloodinium ocellatum. Kills within 48-72 hours when established. Symptoms: gold-dust appearance on body and fins, rapid breathing, flashing.
Causative organism: Amyloodinium ocellatum
Severity: Critical (high mortality)
Velvet kills fast. Within hours of identifying gold-dust appearance, all fish must be moved to a separate hospital tank for copper treatment. Display tank stays fishless for 76+ days to break the parasite life cycle.
Bare-bottom 20-40 gallon tank with cycled sponge filter, heater, no carbon, salinity matched to display, temp 76-80°F.
Increase copper concentration over 24-48 hours. Test daily with Hanna or Salifert copper test - copper degrades in saltwater and must be maintained.
Velvet treatment runs longer than ich. Maintain copper for at least 30 days, ideally 35-45.
Without fish hosts, the velvet life cycle dies out. Inverts, coral, and snails are immune. Display continues running normally minus fish.
After 30+ days copper + 1 week off medication observation period without symptoms, drip-acclimate fish back to display parameters and net into the cleared display.
Marine Velvet is preventable in 95%+ of cases by running a 4-6 week quarantine on every new fish before introduction. Read the quarantine protocol.
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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