Short answer: goldfish are opportunistic omnivores and will eat newt eggs, tadpoles and larvae, and they can bother or outcompete adult newts. Adult newts are usually too big or distasteful to be eaten, but keeping the two together is generally not recommended.
What goldfish will eat
Goldfish eat almost anything that fits in their mouths: algae, plants, insects, snails, eggs and small young animals. In a pond, that includes newt eggs and the free-swimming larvae. Newts lay eggs one at a time on plant leaves, so goldfish can wipe out a whole season of breeding.
Adult newts are not a typical goldfish meal. Many newts also produce skin toxins that make them unappealing. But there are still problems:
- Egg and larva predation. Fish are one of the main reasons ponds with fish have fewer amphibians.
- Competition for food. Goldfish are greedy and fast. Newts can be out-eaten.
- Temperature differences. Many newts prefer cooler water than fancy goldfish do, and some species need to leave the water for land part of the year.
- Water quality. Goldfish produce a lot of waste, and newts are sensitive to poor water.
- Disease risk. Different animals can carry different parasites and pathogens.
- Wild newts are often protected. In some places, including the UK for great crested newts, it is illegal to disturb or capture them, so a pond with wild newts should be left alone.
If you want both
- Use a large pond with dense planting and plenty of hiding places on land and in the water.
- Separate breeding areas. A small fish-free pond nearby gives newts a safe place to lay eggs.
- Do not mix pet newts and goldfish in a small tank. Keep them in separate setups.
- Keep the water clean and test ammonia and nitrite regularly.
Related reading
See what to feed newts in a pond, what crested newts eat and the best food for black moor goldfish.
For sick or injured animals, contact an aquatic or exotic vet.
Bottom Line
Goldfish will eat newt eggs and small larvae, and the two species have different needs, so it is best to keep them apart. A fish-free pond area gives newts the best chance to breed.
