Alder cones are commonly used in aquariums for their natural tannins, which can help create a more natural environment for fish and other aquatic organisms. When added to an aquarium, alder cones release tannins into the water, which can lower the pH level and create a more acidic environment. This can be beneficial for fish that prefer lower pH levels, such as certain species of tetras, discus, and angelfish. In addition to creating a more natural habitat, the tannins released from alder cones can also have other benefits for aquarium inhabitants. They can help to reduce stress in fish and may help in the successful hatching of many species of fish. Alder cones can also provide a natural source of food for some species of aquatic invertebrates, such as shrimp and snails, which can help to keep them healthy and well-nourished. Overall, the use of alder cones in aquariums can be a natural and effective way to improve the health and well-being of fish and other aquatic organisms.