Converting Hans-Werner's results to ounces and cups to compare to Mike's: > 1 Liter of this dry substrate into a pot, the bottom and drainage holes respectively covered with a net (so no substrate will escape after rinsing) WEIGH it before and after RINSING and DRAINING thorougly, the whole container will become 500 grams heavier. > 1 Liter of dry SERAMIS, in the same "experiment" becomes 250 grams heavier. By my calculation, Hans' coir retained 4.2 oz water per half cup and his seramis retained 2.1 oz / half cup. So, if Im correct, then coir retains 4.2 times as much water than Mike's #2 sand (at 1 oz water per half cup) and seramis retains 2.1 times as much water as the sand. This would indicate that coir retains a lot more water than peat. I would welcome someone's scrutiny of my calculations. Corrections welcome! - Gastil