March 21, 2025, 3:29 pm | Read time: 5 minutes
The stickleback is a small fish characterized by its conspicuous spines and unique reproductive behavior. Despite its small size, it is a fierce swimmer that scares off predators with its movable dorsal spines. The stickleback is also extremely adaptable and can survive in both fresh and salt water. Find out below what you need to keep and care for them at home.
The three-spined stickleback is not only a common fish found across the globe, but it is also among the few fish species known for actively constructing nests and providing parental care to their offspring. While many fish simply spawn their eggs in the water, the male stickleback takes on an unusual role: it builds a nest from plant fibers, defends it aggressively against intruders, and uses its fins to ensure a continuous supply of fresh water to the eggs. This special care makes it an exciting object of observation — whether in its natural habitat, in a garden pond. or in an aquarium. Despite its robustness, there are a few things to consider when keeping this cold-water fish. What specific conditions are required, what type of food does it prefer, and what challenges might arise in its care?
Origin
The three-spined stickleback is found throughout the northern hemisphere, from North America to Europe and Asia. Originally, it was a purely marine fish, but over time, it has also adapted to life in fresh and brackish water. Today, it can be found in coastal regions as well as in rivers, lakes, and canals. Its ability to survive in heavily polluted or low-oxygen waters is particularly remarkable — an advantage that has enabled it to form stable populations even in regions with high levels of environmental pollution.
Historically, the stickleback was once caught in large quantities and processed into fishmeal or fertilizer. While it no longer holds economic significance and is not actively fished, the stickleback is of great interest to environmental researchers because its adaptability serves as an indicator of water pollution. Although its populations are declining in some regions, the species is not considered endangered overall.
Appearance
The three-spined stickleback has an elongated, laterally flattened body with a shiny silvery base color and darker marbling on the back. Unlike most fish, it has no scales but is armored by bony plates. This armor varies depending on the habitat: while saltwater sticklebacks are often completely covered, freshwater forms only have isolated bone plates. The size also varies depending on the habitat: in freshwater, they grow to 5 to 8 centimeters, and in salt water, up to 11.
The stickleback’s most distinctive features are its three movable dorsal spines and the pointed spiny rays on its ventral fins. These can be raised in case of danger and serve as an effective defensive weapon against predators. During the spawning season, the appearance of the males changes drastically: their throat and chest turn bright red, while the back appears in a shimmering blue-green.
Behavior
Sticklebacks are lively and curious fish that live together in loose groups outside the spawning season. They are adaptable and tolerate different water conditions, but prefer structurally rich waters with dense vegetation. In aquaria or ponds, they often exhibit shy behavior, but this subsides over time.
In the breeding season, male sticklebacks become highly territorial and exhibit aggression towards both their own species and other fish that venture near their nests. Outside of this time, however, sticklebacks are considered to be peaceful schooling fish that can be easily associated with other small fish species such as minnows or bitterling.
The natural behavior of sticklebacks makes them exciting objects of observation. The courtship behavior of the males, which consists of zigzag movements and color changes, is particularly fascinating. In aquariums and ponds, sticklebacks can be kept busy with live food or by simulating the current. Adding plants and stones to the tank creates a more naturalistic environment, encouraging the sticklebacks to exhibit their innate behaviors.
Correct Keeping & Care
Maintaining sticklebacks is relatively straightforward, though it does necessitate some fundamental care practices. A cold-water aquarium of at least 80 cm long or a pond with a depth of at least 60 cm is ideal. It is feasible to keep sticklebacks outdoors in a garden pond throughout the year. However, the pond should be at least one meter deep so that the fish can stay in the lowest water area in the event of frost. However, this should not be colder than 4 °C.
As a cold-water fish, it tolerates temperatures of 4-22 °C, with 18-20 °C being optimal. If kept in a garden pond, they should be kept in a shady spot so that the water does not heat up too much in summer. Although sticklebacks are robust, they react with stress to water that is too warm. They also do not tolerate a lime content that is too high in the water and corresponding water hardness. Regular water changes are important when keeping them in an aquarium.
Herbaceous and dense aquatic plants are suitable for planting in ponds and aquariums. Hornwort and milfoil, in particular, offer the stickleback hiding places and protected spawning grounds.
Diet
Sticklebacks are carnivores and prefer a varied diet:
- Live food: insect larvae, worms, small crustaceans.
- Frozen food: Artemia, mosquito larvae, water fleas.
- Natural prey: tadpoles, fish fry, fish spawn
Sticklebacks typically reject dry or flake food, making a diet of natural or frozen food the recommended choice.
Susceptibility to Certain Diseases
Despite their robustness, sticklebacks can be susceptible to the following diseases:
- Velvet disease: a parasitic infestation that manifests as a golden brown coating.
- Fungal infections: often the result of poor water quality or injuries.
- Salmon lice: A parasite that attaches itself to the skin of the fish.
Consistent water maintenance, proper feeding, and creating an environment that closely mimics their natural habitat are key to preventing diseases.
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The Three-Spined Stickleback at a Glance
- Scientific name: Gasterosteus aculeatus
- Size: 5-8 cm (freshwater), up to 11 cm (saltwater)
- Life expectancy: 2-3 years
- Special features: Three dorsal spines, no scales but bony plates
- Habitat: Northern hemisphere, in both fresh and saltwater
- Temperament: Peaceful outside the spawning season, territorial during reproduction
- Diet: Carnivore, prefers live and frozen food
- Keeping: Possible in cold-water aquariums or ponds, with dense planting