Adding a SubstrateSource "Medium Marimo Ball" (Cladophora aegargrophila) to your freshwater aquarium helps create a natural look for your tank. As it grows, this 2" (approximate diameter) algae ball helps purify your water by absorbing nitrate nutrients. For optimal growth, occasionally rotate the ball so that it receives light on all sides. Marimo balls make great additions to betta bowls! NOTE: Never release plant species into the wild. Before discarding excess growth, allow the plants to fully dry. Photo depicts sample plant, not the actual plant you will receive. Some discoloration may occur during shipping due to the absence of light during transit.