The first time I saw Velvet I almost panicked and dumped in every medication on the shelf. That would have made it worse. The good news: most cases are treatable at home if you act in the first few days.

The symptom

A gold dust sheen with clamped fins and rapid breathing in dim light.

What is actually causing it

Ranked by likelihood:

Test the water first; treat the cause, not just the spot. A a solid amazon sword care: the classic background plant makes the numbers obvious.

The treatment

Step by step:

  1. Move the sick fish to a hospital tank if you can — see our aquarium air pump guide: oxygen, flow and bubble walls guide.
  2. Raise the temperature slowly to 30 °C to speed the pathogen's life cycle (species permitting).
  3. Add 0.1% aquarium salt, dissolved first, and keep it stable with a 35% water change every other day.
  4. Follow the medication label exactly; overdosing does more harm than the disease.

Prevention

Quarantine every new fish for 3 weeks, keep nitrates under 20 ppm, and avoid overcrowding. Stability is the best medicine — a tank that holds its parameters rarely sees outbreaks.