I agree that it looks unnatural, not because of the colors, but the overall shape of it. Personally, I’m not a fan of arches and NSAs. I like my scapes to be somewhat asymmetrical, I like overhangs or arches that don’t connect, I like (for lack of a better term) canyons where there are sort of walls of rock on either side (leave enough room for corals to grow in on these walls), and I like to leave a network of holes in the rockwork where you can’t really see inside (I like it when fish just sort of pop out of the rockwork). I’m also not opposed to just piling it up in a couple piles/bommies. I just never want it to look designed or man made. But it’s your tank, so do whatever you think looks cool.
Also, the different colors of rock would look much better and more natural if they weren’t used like color coded building blocks (this ties into the symmetry), as it looks kind of like some prefab IKEA aquascape where the different parts are color coded (if that makes sense). *I don’t think IKEA sells prefab aquascapes….yet.
