Starter MINI BLOCKS can sit in a tray (flat) without support for easy starting of seeds and cuttings. They are individually wrapped to minimize algae growth. For best results put them on the flat side of the Tray to ensure good airflow around the cubes. Remove wrapping and transplant into any loose media such as GROW CUBES or GROW CHUNKS, or leave wrapping on and set on top of a larger GRO BLOCK . These cubes are popular for production of aquatic plants. The advantage MINI-BLOCKS have over Starter Plugs and MACROPLUGS is that MINI BLOCKS can sit in a tray without support.