Your fish may have Goldfish Ich (Goldfish Ick)if it has tiny white spots all over their body and they show signs of illness like rubbing up against ornaments, loss of appetite or fin clamping. Ich is also known as White Spot Disease.
This goldfish disease is caused by a single-cell parasite, Ichthyophthirius multifiliis. Many medications are available at your local or online pet store to treat your infected fish.
Note: Male goldfish can develop white spots on their heads during breeding times in the Spring. These fish are healthy and behave normally.
Also: If you keep your goldfish in a pond where mussels also live they may be mussel larvae implanted on the fish. These can appear as white dots. The Larvae will resolve on their own. No medication is needed. These fish will also behave normally.