Pond flow-through filters, also known as gravity-fed filters, are an effective and low-maintenance option for keeping your pond water clean and healthy. These filters are designed to rely on gravity to push water through multiple filtration stages, including mechanical and biological filtration. They work by connecting to an external pump that circulates water through the filter, which is typically placed above the water level. These filters are suitable for smaller ponds and are ideal for pond owners who want a low-maintenance filtration system that provides effective results.