Abstract: Disclosed herein is a system for circulating fluid in an algae cultivation pond. The system includes an algae cultivation pond having an aspect ratio of length to width between 0.7:1 to 2:1, and the pond is at least 5 acres in overall size. An island has a first side and a second side and is positioned in the pond to create a first channel adjacent the first side of the island and a second channel adjacent the second side of the island. An energy input means is located in the first channel and moves fluid around the island through the first channel and through the second channel. The second channel is at least three times wider than the first channel, and a length of the island is at least six times larger than a width of the island.