If you have an established seahorse tank with other inhabitants, it is common practice to quarantine new seahorses for a day prior to adding them to your tank.
When you collect your seahorses from your aquarium dealer, take a temperature reading of the water they are in and then check your tank/quarantine bucket temperature. If there is a major difference float the bag in your quarantine bucket/tank until they adjust.
If these are your first seahorses, they can be added to the tank once you have ensured all your parameters are at the recommended optimum keeping requirements. Never add any foreign water (e.g. the water in the bag your seahorses came in) to your tank.
It may take a day or two for them to settle into their new environment. They may not be very active or feed immediately.
Stocking Densities: The following are the minimum recommendations for stocking your seahorse tank. When purchasing your seahorses, it is important to find out what size they will grow to. You also need to make allowance for any tank mates you might want.
Even though juvenile seahorses can be stocked at higher densities two or three times higher than the recommended adult rates below, it is important to remember that they will grow and you will not want to be replacing your tank every year.
Small Species: (e.g. H. breviceps) < 10 cm adult height - 1 pair adult per 15 liters (5 US gal)
Medium Species: (e.g. H. kuda, H. whitei) < 16 cm adult height - 1 pair adult per 30 liters (10 US gal)
Large Species: (e.g. H. abdominalis) > 18 cm adult height - 1 pair adult per 50 liters (15 US gal)