I firmly believe that the same rules apply to any size tank.
I firmly believe that the same rules apply to any size tank. The only difference is going to be scale. Instead of huge rocks break them up to create a smaller version of the beautiful reef tanks you see. There's other things to try to still get that "look" In a cube the issue is theres not enough length to do multiple structures. Thats when you only do one. Rule of thirds still applies but only use one intersected point instead of two.