What kind of set up is it? Planted, fish only? First I'd up your danios to 6, then you could do Angelfish 2-4, Honey, Dwarf, or a Pearl Gourami, a couple schools of fish such as 6-8 Cardinal, Rummynose, or White Skirt tetras. A group of 6-8 Cory Cats or Kuhli Loaches. Or if not those you could do 3 Yo-yo loaches. If you don't like angels you could do a nice Rainbowfish tank, they come in so many colors. Rainbows, yo-yo loaches, and the giant danio would give you a very active tank.