The Best Pond Sealant - Beware of Imitators!
Concrete based ponds need the final render sealing to stop the water getting in and lime leaking out. G4 has been long established as the market leader for this task. You need 3 coats of clear G4 when you apply it to a pond. This is a total of 550g per square metre. There is enough sealant in a 5kg tin for 9sqm (eg, a pond of 2m long x 1m wide and 1m deep = 8sqm)
You may be new to pond keeping or your pond may be in its twentieth year, but all of a sudden you might start to notice Blanket Weed invading your pond.