When choosing your fiberglass filter unit, take into account the surface area of the filter in relation to the surface area of the pond. The surface area of the filter has to be one third the area of the pond to work effectively.
Water from the pond enters the unit from the right most chamber where you can find filter media such as Flocor (pictured above).
The three 4″ pipes are the connections to the three bottom drains.
The middle sections contain supports for the media trays, which are flat and lay over the top. You do not need this tray if you’re using matting, but if you’re using heavy media like Alpha-grog then you do.
The left most chamber contains brushes.
In the last bay there should be suction for the pond pump. This should have some type of basket so that leaves, debris, or filter media is not drawn in.
Installing a fibreglass filter unit
If you plan to install a large fiberglass filter unit, remember that you will need to stand the unit on a level concrete base with the correct height. This is because the level of the water in the pond is influenced by the final height of the water in the filter (with the vortex chamber if you want to fit one in).
They do not need to be filled around outside as are meant to be free-standing.
The concrete base that you use should be the same mix as the pond base, and that is 3 parts chippings, 2 parts sand, and one part cement. Lay 6 inch deep concrete reinforced with mesh.