Eurasian Ruffe (Gymnocephalus Cernua)

Coldwater Eurasian Ruffe Fish (Care,Feed,Breed Guide)

Eurasian Ruffe (Gymnocephalus Cernua)

Eurasian Ruffe (Gymnocephalus Cernua)

Eurasian Ruffe Fish has been introduced accidentally into many areas outside its native range including the Great Lakes of North America and Southern Europe. In both those areas, the presence of these fish is cause for concern, especially as their population moves south.

Quick Guide:

  1. Origin:
    • England
    • Northern Europe in rivers and estuaries along the North Sea.
  2. Size:
    • in brackish water, they can grow to 8 inches/ 30cm.
    • but in freshwater, they stay around 4.5 inches/ 12cm
  3. Temperature: Room temperature is fine.

Usually, I choose to fish for these coldwater casefile posts that have bright flashy colors. But just because a fish isn’t glowing with all the colors of the rainbow, doesn’t mean that it is a poor choice for a home aquarium. The Ruffe is a perfect example of this.

Physical Appearance:

While its body color, though variable, will never win any beauty prizes, the body has that amazing dorsal fin and the general body shape is different from many other cold water fishes that are suitable for aquarium life.

Fish Care

It is also very easy to care for. If you want a better color than the fish pictured, try keeping them over a light colored substrate. That often results in a light green/brown fish with many dark speckles on the body.

Tank Setup and size:

They can inhabit and breed in both fresh and brackish water. For aquarium purposes, pure fresh water may be better as the fish tend ti stay smaller and easier to house. A pair raised in freshwater could be housed in a 100liter/ 30-gallon tank.

Diet:

In nature, they feed near the bottom on aquatic insects and other invertebrates. The can adapt to prepared foods, but it is best to give them regular feedings of live or frozen bloodworms, brine shrimp, mosquito larvae and even small or chopped earthworms.

Habitat:

Variable, but they never occur in places with rapid water movement. They can be kept in brackish water as high as 1.010 salinity. You can decorate as you wish, but consider adding some dried tree leaves to sink to the bottom. The fish often lounge among these. Their extended dorsal fin looks a lot like a leaf in these conditions and the fish will feel more secure.

Breeding:

They tend to gather in large numbers for breeding. The females lay long strings of eggs that stick to anything they touch. Fry are very small upon hatching and should be fed green water or infusoria. They canĀ breed in both fresh and brackish water

In their native range, the fish mature after 2 or 3 years and each female produces 1000-6000 annually when spawning.

But in warmer climates, they can breed from their first year of life and multiple times per year.

Wikipedia states that each female can lay up to 200,000 eggs per year, but I wonder if they mean over the course of the fish’s life which is 7 to 11 years.

The more modest numbers I gave are from a book called Britain’s Freshwater Fishes by Mark Everard.

If you choose to keep these fish, you likely have to catch them yourself, so check with local laws first. If you do keep them, be careful of the dorsal! Those spines are not just for decoration!

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