Any time I read "sand" in the context of potted plants, I substitute "grit". At least 1 mm in diameter, preferably 2.5 mm.
Or shredded bark. Coarsely shredded bark keeps the surface quite dry, but I wonder about adult gnats crawling between the bark chunks to reach moist soil mix.
I agree with Tiffany:
>> Sand on the surface will migrate down into any tiny air spaces whenever you water, possibly causing roots to suffocate & rot (overwatering) over time. ...
>> putting tiny particles like sand in pots is a recipe for inviting root rot.
At one time, I shopped around for "coarse sand". The coarsest sand I ever found was still 60-70% "fine or medium".
Sand can benefit outdoor soil but I don't think it has a role in soilless container mixes, which need faster drainage than outdoor soil.
