Gold dust

Fine gold or rust-coloured dust on the body — may indicate Velvet (Oodinium), visible under side light. Compare your fish with the reference photo above and cross-check your logged parameters in Aquarium Tracker before medicating.

SymptomGold dust

CausesParasitic dinoflagellate often triggered by stress / Introduction without quarantine

TreatmentDim lights — velvet photosynthesises and is easier to observe in low light / Improve water quality and stabilise temperature

PreventionQuarantine new fish; zero ammonia & nitrite

What causes gold dust?

Parasitic dinoflagellate often triggered by stress
Introduction without quarantine
Temperature instability
Prolonged poor water quality

What to check before medicating

What to measure	Typical target	What an off reading points to
Temperature	within your species range, steady	Warmer water holds less oxygen and speeds both metabolism and pathogen growth. Sudden swings stress fish more than a steady figure at either end.
Ammonia (NH₃/NH₄⁺)	0 ppm	Anything above zero means the biological filter cannot keep up. Toxic to fish long before it is high enough to feed algae.
Nitrite (NO₂⁻)	0 ppm	A reading above zero points to an immature or disrupted filter — common after a media change, medication, or a large clean.
Recent changes	note anything from the last 2–3 weeks	New livestock, plants, media, lighting or dosing are the usual trigger. The cause often precedes the symptom by a fortnight.
Stocking level and mix	suits volume, footprint and temperament	Crowding raises waste and stress together, which is why disease often follows a new addition rather than a parameter change.

Take these readings first. A large share of what looks like disease is a water quality problem, and medicating a tank whose ammonia is climbing treats the symptom while the cause keeps working.

Treatment steps

Dim lights — velvet photosynthesises and is easier to observe in low light
Improve water quality and stabilise temperature
Quarantine and treat with appropriate copper or formalin-based medication — many are toxic to invertebrates and plants
Treat the whole tank if multiple fish show symptoms
Consult a specialist for medication compatible with your livestock

Prevention

Quarantine every new fish for 4 weeks — this is the single measure that prevents most parasite outbreaks, and the one most often skipped
Quarantine new plants, snails and anything wet from another system; parasites travel in water, not just on fish
Avoid overstocking; crowding raises waste and stress at the same time
Feed only what is eaten in a few minutes, and remove the rest

Frequently asked questions

Is gold dust contagious to my other fish?

Yes, and it spreads faster than ich. Velvet can take a tank down in days, so treat every fish in the system immediately.

How quickly do I need to act?

Within hours. Velvet moves faster than ich and is frequently fatal before keepers accept what they are looking at.

Should I treat in the display tank or a hospital tank?

A separate hospital tank is preferable where the fish is well enough to move: doses are easier to control, and many medications harm invertebrates, plants or the biological filter. Treat in the display only when the whole tank is affected or moving the fish would add more stress than the treatment removes.