Horticultural sand is what you need, the stuff from the beach has too much salt in it. Also, it's all different sizes - I discovered to my cost that "any old sand" packs down to an almost concrete hardness, resulting in virtually zero drainage and roots can't get down into it. Horticultural sand is one grade only so the particles move past each other and don't get jammed in together. You should be able to find it at most garden centres.

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Dwell simply ~ love richly