Pygmy seahorse help!?

Seahorses in general are not beginners fish. They are hard to keep and require a very specialized environment. There are a few saltwater fish you can keep in a 10gal. My recommendation would be a firefish goby or a clown goby. Just add in a bit of live rock and a protein skimmer and you will be fine with the set up you have. (make sure to have a gl canopy though firefish gobies are notorious jumpers) You could also do an invertebrate only tank with , snails, shrimp ect.