Great looking tank! I voted for the montagiís. If youíre really looking for something rare, I think theyíre the way to go. Because of the bright coloration of wadai and cyanotenia, theyíre showing up in more and more tanks- theyíre both gorgeous, but the montagiís are next level IMO. They donít come around often and Iíve only ever seen them in Tanks from Asia- and only in baller tanks with great scapes- I think they would look amazing in your 30 gal as the main school of fish- I like the idea of tucanoís in that tank too- and they would look really cool with the montagiís. If you didnít want to go with a smaller group of tucanos with the montagiís, you could always add 8-10 wadai or cyanotenia for a little color.
Experience: worked in fishroom of Eddies Aquarium in Albany all through college, 20 years of keeping reef tanks, planted tanks, and dart frog vivariums.
Current/in-progress tanks: 20 gallon hi tech tank in office, 120 gallon nature/tetra aquarium at home.
Philosophy: work with what youíve got, and make choices based on the conditions that easiest for you to maintain over time.