G4 Pond Sealer Clear 5kg
If you have decided to make your pond from concrete then you will need to seal the top layer of render to stop the water getting in and the lime, which is harmful to fish, getting out. The best way to do this is with G4 Sealer. You don't need a primer; just paint it straight onto the concrete.
For a clear finish you need three coats - a total of 550g per square metre.