Lined Seahorse
Hippocampus erectus
The Vertical Fragile Dragon (6 inches / 15 cm). Keeping Seahorses is not just fish-keeping; it is an entirely separate, elite sub-hobby. They are mesmerizing, primitive fish that swim completely vertically and possess a prehensile, monkey-like tail used to anchor themselves to seaweeds. However, they are cripplingly delicate. They lack a true stomach, they are incredibly weak swimmers, and they possess zero natural defenses against aggression, stingers, or basic fish competition.
Water Temperature
22 - 26 °C
pH Value
8.1 - 8.4
Water type
Freshwater
Tank level
Middle
Adult size
17 cm
Minimum tank volume
120 L
Minimum group
>= 1
GH
8 - 12 dGH
KH
4 - 6 dKH
TDS
160 - 240 ppm
Conductivity
250 - 375 uS/cm
Species description
Geographical Origin and Habitat: MARINE species native to the Western Atlantic Ocean (from Nova Scotia to South America). Mainly inhabits macroalgae beds, coastal mangroves, and shallow reefs, where it clings to vegetation using its prehensile tail.
Taxonomy and Morphology: Lined Seahorse (Hippocampus erectus). Bony fish (Syngnathidae). Armored body structure with dermal bony rings, tubular snout for rapid suction of prey, strictly erect posture, and prehensile tail without a fin.
Social Behavior: Extremely placid, methodical, and slow creature. Spends hours anchored to gorgonians or algae (hitching posts) analyzing the water in search of food. Forms monogamous bonds and greets each other daily with elaborate dances and color changes.
Coloration and Sexual Dimorphism: Color variable from yellow to brown, black, red, or orange, often with thin white lines on the neck (hence "Lined"). The male is easily distinguished by the presence of a prominent brood pouch (marsupium) under the abdomen.
Care, breeding and tankmates
Aquarium Setup: Specialized marine aquarium (minimum 120 liters / 30 gallons, TALL tank, very slow flow). INDISPENSABLE numerous hitching posts (Caulerpa macroalgae, fake gorgonians, smooth branches). Filters equipped with guards to prevent their tails from being sucked in.
Diet and Feeding: Micro-predatory carnivore with a rapid metabolism (does not have a true stomach). MUST be fed 2-3 times a day. Wild-caught specimens demand live Mysis and Artemia; captive-bred (CB) specimens eat frozen Mysis enriched with vitamins.
Water Quality: Maintain Salinity 1.020-1.025, pH 8.1-8.4, and cool temperature (22-26°C / 72-79°F maximum). Warmer temperatures quickly trigger bacterial proliferations (Vibrio) lethal to seahorses. Skimmer indispensable due to the numerous meals.
Compatibility and Cohabitation: Optimal keeping only in SPECIES-ONLY tanks or with very small and very slow marine fish (e.g. Neon gobies, pipefish). Stinging corals (anemones, Euphyllia), crabs, and fast fish would compete for food or fatally injure them.
Aquarium Breeding: Frequent in healthy specimens. The female transfers eggs into the male's pouch who undergoes the pregnancy. After 2-3 weeks the male "gives birth" to dozens/hundreds of perfect tiny seahorses, which require constant rotifer cultures.
Risks and Diseases: Very delicate. Susceptible to Gas Bubble Disease where bubbles form under the skin, lethal if untreated. Vibrio infections will decimate the tank if the temperature exceeds 26°C (79°F).
Geographic Origin and Distribution
MARINE species native to the Western Atlantic Ocean (from Nova Scotia to South America). Mainly inhabits macroalgae beds, coastal mangroves, and shallow reefs, where it clings to vegetation using its prehensile tail.
Origin
Tropical oceans and reefsExtra-Amazon South AmericaCentral America and Caribbean
Fish profile
- Temperament
- Semi-aggressive
- Seahorses are extremely docile, curious, and incredibly peaceful marine creatures. They show absolutely no aggression toward other fish species and only minor courtship posturing among themselves. Their calm demeanor requires an equally calm environment to prevent them from becoming overwhelmed. They observe their surroundings meticulously and interact gently with their environment.
- Diet
- Omnivore
- Seahorses are strict carnivores that feed almost exclusively on small crustaceans like mysis shrimp. Captive-bred individuals are usually trained to accept frozen mysis, which forms the core of their diet. Food should be enriched with lipid and vitamin supplements to prevent nutritional deficiencies over time. Wild-caught specimens often refuse frozen food and require a constant supply of live foods.
- Life expectancy
- 1-4 years
- The lifespan of the lined seahorse in captivity usually ranges between 1 and 4 years. This period can be maximized by keeping the aquarium water clean and free of bacterial pathogens. Regular water changes and controlled chemical filtration help prevent lethal infections of the snout and skin.
- Adult size
- 17 cm
- The catalog's scalar value is 17 cm. The FishBase species summary source reports a maximum adult measurement of 17.8 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Hippocampus erectus (live-2026-07-30); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Pair
- Males can be distinguished by the presence of a brood pouch located at the base of their abdomen. Females have a smoother profile and generally maintain a slightly more streamlined shape. They are best kept in male-female pairs or small groups of mixed sexes. They are highly social with their own kind and form strong pair bonds over time.
- Feeding frequency
- Twice daily
- Because they lack a true stomach, food passes through their system very quickly, requiring almost constant grazing. They must be fed small amounts at least two to three times every single day. Creating a designated feeding station can help ensure they get enough to eat without the food blowing away. Skipping meals can lead to rapid weight loss and compromised health.
- Bioload
- Seahorses produce a surprisingly high bioload despite their delicate appearance due to their inefficient digestive systems. They require large amounts of frequent, meaty feedings which quickly degrade water quality. Excellent filtration and diligent maintenance, including frequent water changes, are strictly mandatory. A high-quality protein skimmer is essential to remove dissolved organics before they break down.
- Flow
- Stagnant
- They demand very gentle, low-flow water movement that allows them to swim and hunt comfortably. Strong currents will exhaust them and blow them around the tank, leading to severe stress. Flow should be diffused, ensuring there are no dead spots while keeping the overall current mild. Providing plenty of hitching posts in calm areas is crucial for their resting behavior.
- Reproduction
- Oviparous
- Seahorses have a unique reproductive cycle where the male carries the eggs in a specialized brood pouch. After a complex courtship dance, the female transfers her eggs to the male, who fertilizes and incubates them. The male eventually gives birth to hundreds of fully formed, miniature seahorses. Raising the fry requires dedicated culturing of rotifers and freshly hatched baby brine shrimp.
- Compatibility & tankmates
- They are extremely passive and slow-moving, making them highly vulnerable to aggressive or fast-swimming tank mates. They should only be kept in dedicated species-only tanks or with extremely docile companions like pipefish and small gobies. They cannot compete for food with quick fish and will likely starve in a standard community reef. Stinging corals and aggressive invertebrates must also be completely avoided.
- Tank level
- Middle
- They heavily utilize the vertical space in an aquarium and require tanks that are much taller than they are wide. They spend their days hitched to macroalgae, artificial corals, or gorgonians in the lower and middle levels. They rarely swim in open water, preferring to camouflage themselves among vertical structures. Adequate hitching posts throughout the vertical column are completely essential.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.5 ± 0.51 se
- Resilience
- High (less than 15 months)
- Generation time
- 3.2 years
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.00447, b = 3
- VulnerabilityLow to moderate vulnerability (31 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
