I have the same tank. since you have a lid (wish i had one) i would do 10 or so Clown killifish or furcata rainbow. The furcata's are my favorite fish and they love the swim room on this tank and if you only keep furcata's they will breed for you. Another fish i have loved in this tank is ember tetra's. Feed them food with carotenoids in it like cyclop eeze or similar and watch them turn deep deep orange/red.
p.s. Would you mind sharing the specs and rough cost of your lid? I need to get one made fish really like to jump with this tank.