The seahorse will do much better in a biotope style or species specific tank. In general the seahorse needs things to hold on to with their tails. They prefer low water flows and they need to be fed often with defrosted or live foods. They can be considered more challenging than saltwater fish.
Hippocampus kuda Common Seahorse The seahorse really does best in a species only setup where you can provide them a high quality diet of mysis shrimp and other smaller crustaceans. It's challenging to keep the seahorse with other fish species because they are very slow eaters and they appreciate more moderate currents than those found in typical saltwater setups or reef tanks.
Hippocampus kelloggi Great Seahorse Can grow up to 11 inches (28 cm) and needs a larger tank with plenty of holdfasts. Provide a high quality diet and maintain excellent water parameters.