We're all pretty familiar with the wonderful Alder Cone, which has been widely utilized by aquarium hobbyists for some time. You've probably not seen the incredibly useful cones from the Casuarina equisetifolia, or "Australian Pine Tree" before! We certainly hadn't, until one of our Indian suppliers told us about them! The native range of this tree is vast, extending from Southeast Asia throughout Oceana, and of course, Australia. Non-native introductions of these trees are found in Madagascar and India.
These little cones have been used in the hobby for years, much as Alder cones have, and they're pretty "high performance", from a tannin-producing perspective. They're larger, generally "fatter", and they tend to break down quite a bit more slowly than Alder Cones, in our experience.
We'd recommend a starting quantity of about 6-8 for every 60 liters of aquarium water, although there is no hard and fast rule about this. Casuarina Cones can lower the pH of soft water surprisingly quickly while imparting a nice brownish tint.