What Is Goldfish Roe & Milt?

When looking into caring for or breeding goldfish, you may run across some terms you are not familiar with, such as roe and milt. Understanding these terms and how they relate to the goldfish can help you successfully breed your fish.

  1. Roe

    • Roe is another term for the eggs of the goldfish. Female goldfish carry the eggs until they are ready to breed. This is often one of the best ways to determine gender in goldfish. When the female is full of roe, the fish often appears much pudgier or rounder than the male goldfish in the aquarium.

    Milt

    • Milt is the fluid of the male goldfish, which carries the sperm of the fish. The male goldfish releases this fluid during spawning, thus fertilizing the eggs.

    Breeding Behavior

    • Before breeding, the female goldfish swells with roe. The female fish's vent also swells a bit and turns slightly out, indicating the fish is ready to breed. Male goldfish develop tubercles, which resemble small, raised white spots, on the gills and along the edges of the pectoral fins.

    Spawning

    • After the initial breeding behavior and rituals, the goldfish will spawn. This can occur a few days after the male and female goldfish are placed together, and only happens when the water conditions are correct. Goldfish can breed when the water is anywhere between 50 and 78 degrees Fahrenheit, but breeding usually occurs when the water temperature is right around 68 degrees. The fish also need to feel they have enough space, with about 15 gallons of water for each fish. When they have completed their pre-spawning behavior, the female goldfish will release a batch of roe. The first batch released is usually the most fertile. The male will then release the milt over the roe, fertilizing it. This spawning behavior can be repeated several times, with the female laying many batches, which the male continues to fertilize. Anywhere between 500 and 1,000 eggs can be laid and fertilized before the breeding is over.