Lined seahorse (Hippocampus erectus) care guide

Group
Marine fish
Family
Syngnathidae (seahorses and pipefishes)
Water
saltwater
Maximum size
19 cm
Temperature
20–24°C
pH
8.1–8.4
Hardness
Salinity SG 1.023–1.026
Minimum tank
110 litres
Care level
intermediate
Temperament
peaceful
Reef safe
with_caution

Care

Tank and decor: seahorses need a tall rather than long tank with gentle flow and plenty of hitching posts such as macroalgae, artificial gorgonians or branches. Avoid strong pumps and cover intake strainers. Minimum tank: about 110 litres for a pair (an estimate based on its 19 cm adult size and need for height). Water: the list marks this species as subtropical. Our sources give no further figures, so the values here are general marine aquarium guidance, not species-specific: 20–24 °C, pH 8.1–8.4 and specific gravity 1.023–1.026. Seahorses are very sensitive to poor water quality and to bacterial infections, so keep the tank clean and well filtered. Identification: the list describes it as dark with a lighter belly and white ridges. It is a hardy subtropical species and captive-bred stock is often available. The list gives a maximum size of 19 cm. All seahorses (genus Hippocampus) are listed on CITES Appendix II. In Great Britain, CITES Appendix II species are Annex B under the wildlife trade regulations, so sellers must be able to show the fish was legally imported or captive-bred and keep the paperwork. Captive-bred seahorses are strongly preferred: they settle better and usually accept frozen food. Sources: Wikipedia, List of marine aquarium fish species (en.wikipedia.org/wiki/Listofmarineaquariumfishspecies). Checked October 2026.

Diet

Feeds on small live crustaceans in the wild. In captivity give enriched frozen mysis shrimp two or three times a day; captive-bred seahorses usually take frozen food readily, while wild-caught ones may need live mysis or enriched brine shrimp at first. Seahorses have no stomach to store food, so they need frequent small meals. Remove uneaten food promptly.

Breeding

As in all seahorses, the male carries the eggs in a brood pouch and later releases fully formed young; there is no further parental care. Pairs often greet each other with a daily courtship display. The fry are tiny and need live food such as rotifers, copepods or newly hatched brine shrimp, and are best raised in a separate tank. Our sources for this page give no further species-specific breeding details.

Compatibility and tank mates

Reef safe with caution: seahorses do not harm corals, but they can be stung by anemones and aggressive corals and may lose out to fast-feeding fish. Keep them in a species tank or with small, calm tankmates such as small gobies and pipefishes. Avoid crabs, anemones, large shrimps and any fish that nips or competes hard for food. They will eat very small shrimps.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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