Tonic Studios Nuvo Aqua Flow. This pack is the Water Brushes which comes with two water pens. Nuvo Aqua Flow pens are uniquely designed to create a watercolor effect without the hassle and mess. These highly pigmented water-based pens leave you with a bright, vibrant finish. The perfectly formed watercolor brush nib makes the pens extremely versatile and is perfect for adding small detail or color washing large areas. Each pen has its own reservoir complete with a non-drip valve.