Oh, the lengths we go to, trying to build a nest. Published in Nature, this open-access article talks about large circular structures pufferfish build, just to attract the opposite sex.
…male pufferfishes (Torquigener sp., Tetraodontidae) constructed large geometric circular structures on the seabed that played an important role in female mate choice. Males dug valleys at various angles in a radial direction, constructing nests surrounded by radially aligned peaks and valleys. Furthermore, they created irregular patterns in the nest comprising fine sand particles. The circular structure not only influences female mate choice but also functions to gather fine sand particles in nests, which are important in female mate choice. Strangely enough, the males never reuse the nest, always constructing a new circular structure at the huge cost of construction. This is because the valleys may not contain sufficient fine sand particles for multiple reproductive cycles.
Male pufferfish, Torquigener sp. Source: http://www.nature.com/srep/2013/130701/srep02106/fig_tab/srep02106_F1.html