Nice! That tank is a great size. Big enough for a betta to be happy, but not so big that it takes up too much space or looks too big.
My adventures in keeping Indostomus crocodilus, the crocodile toothpick fish. AKA armored stickleback, paradox fish, and freshwater pipefish. Care is (to the best of my knowledge) exactly the same as Indostomus paradoxus.