Seahorse Aquarium Guide: Species, Tank, Temperature and Feeding
Keeping H. erectus, H. reidi and H. kuda: tall calm tanks with holdfasts, published temperature ranges, Vibrio and mycobacteria risks, frozen mysid feeding and tankmate limits.
Species commonly kept
- Lined seahorse (Hippocampus erectus): western Atlantic from Nova Scotia to Venezuela, in seagrass, sponge and mangrove habitats to 73 m; 12–17 cm, recorded to 19 cm. Most animals in the trade are captive-reared. IUCN status Vulnerable.
- Longsnout or slender seahorse (Hippocampus reidi): western Atlantic from the south-eastern United States and the Bahamas to Brazil, on reefs and seagrass beds and among gorgonians, mangroves and sargassum to 55 m; about 17 cm. IUCN status Near Threatened.
- Common or yellow seahorse (Hippocampus kuda): Persian Gulf through South-East Asia to Australia, Japan, Hawaii and East Africa, in estuaries, lagoons, harbours and coastal seagrass to 55 m; 17–30 cm; tolerates salinities of 18–36 ppt. IUCN status Vulnerable.
Legal status and sourcing
All seahorse species (genus Hippocampus) are listed on CITES Appendix II; the listing has applied to trade since 15 May 2004. International trade in Appendix II species requires export permits. CITES advisers recommended a 10 cm minimum height as an interim measure for wild-caught specimens, and this size limit does not apply to captive-bred animals. Wild-caught seahorses usually do poorly in home aquaria: they often accept only live food and are prone to stress-related disease. Captive-bred seahorses accept frozen mysids more readily, carry fewer diseases and do not draw on wild populations.
Tank shape, flow and hitching posts
Seahorses are very weak swimmers; the dwarf seahorse is regarded as the slowest-moving fish, with a top speed of about 1.5 m per hour. Instead of swimming against current they anchor themselves with a prehensile tail to seagrass or other fixed objects. A seahorse tank therefore needs calm water and plenty of holdfasts, such as branching decor, artificial plants or macroalgae, spread through the water column.
Height matters as much as volume. Seahorses need vertical space for courtship, in which partners release their holdfasts and rise together through the water column during egg transfer, and vertical depth is also cited as a way to prevent gas bubble disease. For the lined seahorse, a minimum of 20–25 US gallons (about 75–95 L) is cited for one pair.
Temperature and water quality
Published ranges differ by source and species. A general seahorse husbandry range of 23–28 °C at pH 8.1–8.4 is cited; for captive H. erectus and H. kuda, 22–25 °C is given, with 23–24 °C described as optimal for H. kuda. In Chinese aquaculture H. erectus, whose natural range spans about 20–29 °C, shows optimal growth at 25–26 °C, and juveniles in recirculating systems were reared at 25–26 °C and a salinity of 28–29 ‰. Public aquaria holding syngnathids set temperature and salinity according to each species' native range, use a 12-hour light cycle and disinfect water with UV or ozone.
Disease risks: Vibrio and mycobacteria
Bacterial disease is the main constraint in seahorse culture. In H. erectus farming, enteritis linked to Vibrio harveyi can kill up to 80 % of animals within 3–5 days of the first signs, which include white pus around the anal opening and a swollen abdomen; management relies on good environmental conditions, high-quality nutrition, quarantine and antibiotic treatment. Vibrio splendidus has been reported as a secondary infection at gas bubble disease lesions in syngnathids, and gas bubble disease itself is caused by supersaturation of dissolved gas in the water. Mycobacteriosis, caused mainly by Mycobacterium marinum, M. fortuitum and M. chelonae, is a recurring problem in captive syngnathids; stress, poor water quality, poor management and high stocking densities are associated with higher prevalence. One public aquarium protocol checked water for Vibrio counts every three months.
Feeding
Seahorses are ambush feeders that take small crustaceans, especially mysid shrimp and amphipods. They have no stomach and need to eat frequently through the day; for H. kuda in captivity, four to five small meals a day are cited. Public aquaria feed syngnathids mainly live or frozen mysids and live or frozen brine shrimp (Artemia) enriched with fatty acids. Frozen mysids are the core feed in commercial seahorse culture, but storage affects quality: in one study, two months at −20 °C limited bacterial spoilage yet freeze–thaw damage removed key feeding-attractant amino acids, and after ten months lipids had oxidised and spoilage bacteria, including Vibrio, had multiplied. The authors advise against feeding mysids that have been stored frozen for long periods.
Tankmates
Seahorses are slow, deliberate feeders and should not compete with fast or aggressive fish. Eels, tangs, triggerfish, squid, octopus and sea anemones are listed as unsuitable companions, while gobies and shrimp are given as suitable. Quiet tanks without aggressive species are recommended for H. kuda.