Pressure filters are a popular choice for small and medium-sized garden ponds. They are sealed units that can be positioned discreetly alongside the pond, with many models suitable for partial burial. Because the water remains under pressure, they can also supply an elevated waterfall or water feature, subject to the pump's capabilities. Many pressure filters include a built-in UV clarifier and convenient cleaning systems, making them a practical, compact solution.

Flow-through filters, sometimes called gravity-return filters, are commonly used on medium and larger ponds. Water is pumped into the filter before returning to the pond by gravity. These systems often provide generous mechanical and biological filtration capacity and can be particularly suitable for ponds containing fish. They do, however, require space alongside the pond and must be installed at a suitable height to allow water to return freely.

Drum filters offer advanced mechanical filtration, automatically removing suspended waste and debris through a fine screen. They are particularly popular for koi ponds, heavily stocked fish ponds and larger installations where excellent water clarity and reduced manual cleaning are priorities. Drum filters are often combined with separate biological filtration and UV equipment. Although the initial investment is higher, their automatic cleaning makes them an attractive option for demanding pond systems.

In-pond filters are compact systems designed to sit directly inside the pond. Many combine a pump, filtration, UV clarifier and sometimes a fountain attachment in one unit. They are ideal for smaller ornamental ponds where space is limited or a simple installation is preferred. However, their capacity is generally more limited, making them less suitable for larger or heavily stocked fish ponds.

Pond skimmers help keep your pond clean, clear and healthy by removing floating leaves, pollen and debris before they sink and decompose. Available in various sizes to suit different ponds, options include built-in wall skimmers, freestanding and floating models, with some featuring integrated pumps. They improve water quality, reduce sludge build-up and minimise ongoing pond maintenance.

The volume of your pond is an essential starting point, but it should never be the only consideration. A lightly stocked ornamental pond has very different filtration requirements from a pond containing numerous goldfish or large koi. Fish produce waste, and feeding introduces additional nutrients into the water, increasing the demands placed on the filtration system. When comparing filters, always check the manufacturer's recommended pond capacity for your particular situation. Many manufacturers provide different ratings for ponds without fish, ponds with fish and heavily stocked koi ponds. Choosing a filter based solely on its maximum advertised pond volume can result in an undersized system.

Ponds receiving direct sunlight for much of the day are generally more susceptible to green water, particularly when nutrients are readily available.

A pond in full sun may require a more powerful UV clarifier than a similarly sized pond in a shaded location. Fish stocking levels, water depth, planting and feeding habits also influence algae growth.

Consider how many hours of direct sunlight your pond receives during the summer when selecting your filtration and UV equipment.