This DIY Kit will allow you to build a (2 x 5m pond) at 3 ft deep. Equating to a total of (10,000) litres.
 
Pond kit Matic 10,000 litres -
Pond Dimensions: Length 2m; Width 5m; Depth 1m
Filter Kit: ScreenMatic 40,000 set
Liner: Greenseal 1mm thick 5m x 8m
Underlay: 250 gsm (white)
Total Litres: 10,000 (Approx)
Max Stocking density: 10 x Koi or Larger species
Additional equipment included: Discharge pipe 75mm x 1m / 75mm 90 degree elbow x 1 / Medium Duty
1.5” hose x 5m