Peat moss holds a lot of water so I want to try sand only soil to avoid overwatering. What grain size would be ideal? I could buy 0,2 - 0,8 mm (average 0,5mm). Would roots grow fine and won't it compact? Pot size would be 15 cm. If I would use bigger grain size capillary action won't work well.
I grow cape sundew in mostly 0,5mm with a bit of 1mm sand and it seems to be fine.
Only downside I can think of would be it dries out super fast. I don't think putting it in a tray of water would work to keep it watered either, I don't think sand will absorb it up into the pot. That might leave you to top water only but in the heat of the summer that could become almost impossible I would imagine.
Height of capillary rise depends on grain size. 0,5mm grain size rises to 15cm so it would reach top of the pot. 1mm to 8 cm. Fine sand would rise to 50 cm, but maybe it would be to compacted for roots to grow or too wet.