23rd October 2013 at 7:42 pm #858
When washing river sand, my experience has been that when the water coming off still has a fair bit of turbidity (muddiness), then it still needs to be washed. But after 6 or 7 washings, the water coming off is still kind of brown but a transparent kind of brown – not a muddy / chocolate kind of brown. To me this indicates that the sand is clean enough. So you’ll have to make the judgement yourself, but you don’t want clay and organic matter in your sand, but some colour is probably inevitable.
Be careful when washing sand though that when you decant the water, that you don’t pour off the fine particles. Sand is made up of larger and smaller particles which gives every sand its own characteristic – and it’s the smaller particles which are very important in adding surface area to the filter sand, so you don’t want to lose them when decanting water. It is the small particles sometimes that give the colour to the water too, so when the water isn’t 100% clear it could be due to that.