We have one Savio Skimmers in stock. It is a small compact skimmer-filter (CS0000) that the manufacture says are suitable for a pond of 700 gallon koi pond and 2500 gallon water garden. The two filter trays that are visible can be pulled out and hosed off with pond water when they get filled with small debris. There is a handy leaf basket with a handle directly across from the opening. This leaf basket catches leaves and twigs and can easily be pulled straight up and emptied very quickly.
The pump is placed in the opening behind the two filter cartridges. The hole in the back is for the outflow of the pump and is not designed to be sealed. The round hole serves as a safety valve or water overflow if there is too much water in the pond.
The hole in the center will accept a UV light and is simply installed by placing the light down in the hole and locking the light in with the three slotted openings. The proper water level is maintained by placement of the unit and also by the height of the opening where the outflow of the pump is.