How do you determine the gender of fantail goldfish?

Answer:

Goldfish can only be sexed at breeding time when the males develop white spots on their Gill plates and sometimes their Pectoral fins too. The females simply get chubbier as they fill with ova (eggs).

First answer by EddyJ. Last edit by EddyJ. Contributor trust: 132 [recommend contributor recommended]. Question popularity: 2 [recommend question].