The lined seahorse is a hardy, temperate-to-subtropical western Atlantic seahorse and one of the best species for captive seahorse keeping, especially as a tank-raised animal. All seahorses (genus Hippocampus) are CITES Appendix II listed, so captive-bred stock is both more sustainable and far easier to keep, and international trade is regulated.
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Western Atlantic, Nova Scotia to the Caribbean and Gulf of Mexico
Origin
New World
Climate
⛅ Subtropical
Water type
🌊 Marine
Family
Syngnathidae
Genus
Hippocampus
Part of the Seahorses
Seahorses are slow-moving, prehensile-tailed marine fish of the family Syngnathidae, famous for male pregnancy and pair bonding; they demand cooler, pristine, low-flow tanks and are best kept as captive-bred specimens.
More seahorses coming soon.
Habitat & space requirements
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Photo coming soon
Minimum
Tall species-only tank
30 gal tall / 110 L species-only
Hippocampus erectus needs a TALL tank (≥45 cm) for mating ascents, slow flow (<10× turnover, well-diffused), 22–24 °C, and species-only setup. Pair feed frozen mysis 2–3× daily.
Photo coming soon
Recommended
Cycled seahorse system
45–55 gal tall / 170–200 L
More volume stabilises params for these slow, mess-prone feeders. Add many hitching posts (artificial macro, gorgonian skeletons), a bare or sand bottom, and a deep refugium for pod backup.
Photo coming soon
Ideal
Captive-bred pair display
70 gal+ / 265 L+ tall display
Large tall display with captive-bred pair, oversized skimmer, UV sterilizer (mycobacteria/vibrio risk), chiller for stable 22 °C, and a thriving copepod refugium. Best chance at long life.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
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Egg
Fish eggs are small, translucent spheres, often laid in clutches on plants, substrate, or in a nest — or carried/brooded by a parent in livebearing and mouth-brooding species. A dark eye spot and the curled embryo become visible inside as development progresses.
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Fry
Newly hatched fry are tiny and semi-transparent, frequently still carrying a yolk sac that fuels them before they feed freely. They lack full fin structure and adult coloration, staying near cover until they can swim and forage on their own.
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Juvenile
Juveniles look like miniature adults but with developing fins and muted or different markings; many species shift pattern and color as they mature. Growth is rapid at this stage given clean water and steady feeding.
Adult
Adults show the species' full size, finnage, and mature coloration, and are sexually mature. Many fish develop sex-specific differences in size, color, or fin shape, which can intensify during breeding.
Habitat & enclosure
House a pair in a tall marine tank of at least 30 gallons (taller is better for their vertical courtship and birthing). Keep cooler than a typical reef: 68-75 F (20-24 C), salinity 1.020-1.025 SG, pH 8.1-8.4, with very low flow. Provide numerous hitching posts — artificial or hardy soft corals, macroalgae, and branching decor — for them to anchor their prehensile tails.
Substrate
A bare bottom or thin layer of fine sand is preferred for easy cleaning, since seahorses are messy eaters and detritus fuels bacterial blooms. Keep the substrate spotless to limit Vibrio and other opportunistic infections.
Equipment & setup
A reliable marine filtration system with protein skimmer, gentle flow (avoid strong powerheads and pump intakes that can trap them), a chiller or cool room to hold temperatures down, and quality salt mix with regular water testing. Abundant hitching posts and a tight lid complete the setup. UV sterilization can help control bacteria.
Diet
Carnivorous ambush feeders that eat slowly and frequently. Tank-raised individuals readily accept frozen mysis shrimp, the dietary staple, fed 2-3 times daily; supplement with enriched live foods. Their slow feeding means they cannot compete with fast tankmates, so they need a dedicated, quiet feeding setup, often a target-feeding station.
Behavior & temperament
Slow, deliberate, and peaceful; they hitch by their tails and are poor swimmers easily outcompeted for food. Keep only with seahorse-safe, slow, non-aggressive tankmates (or species-only). They form pair bonds and perform daily greeting dances; the male broods young in his pouch and gives live birth. Not a handleable animal and easily stressed.
Health
Notoriously prone to bacterial infections, especially Vibrio, and to gas-bubble disease; impeccable water quality and cooler temperatures are essential to suppress pathogens. Snout and pouch infections, weak hitching, and refusal to eat are warning signs. Wild-caught animals often arrive stressed, parasitized, and hard to feed — buy captive-bred. Quarantine and a knowledgeable vet are valuable.
Tips, DIY & hacks
Always buy captive-bred (tank-raised) erectus; they eat frozen mysis, tolerate captivity, and avoid the conservation harm of wild collection. Keep them cooler than reef tanks to suppress Vibrio. Feed frozen mysis multiple times daily and keep the tank meticulously clean. Choose only slow, peaceful tankmates. Be aware seahorse keeping and trade are regulated under CITES Appendix II.
