If I may add my two cents on the background issue... I ALWAYS say 'no paint!'.
You never know when you might change your mind about background color... or (since you use natural rock for decor) if you sustain a nasty scratch on the front wall of your tank, you can't flip it around and use the unblemished side because it's painted. so I'd say buy a length of black from your local petshop or aquarium store and tape it on.
And even though I generally prefer a natural substrate, I could see that blue becoming something truly unique and interesting with the right artistic touches. I saw a similar gravel used to decorate an aquarium that was adorned in large, braced pieces of red and black colored sea glass and kitchen whisks (coated in waterproof sealant, of course!!). They kept two white angelfish, albino danios, neons, albino corydoras, and a bristlenose plecostamos. Very 'extra-terrestrial'!!
But I tend to take a very artistic approach to these sorts of things... ^_^;;