just by weight cheryl. feel 1 cube which hasnt been used and is dry. then pick up the seedling cube, notice any difference? when watering just plonk the bottom half of the cube in some water for about 2 secs. also if u have trouble with dampness etc a gd little tip ive found out is to place the cube above another 1. this way the cube below sucks alot of the water out. altho this way u have to check every 6-7 hours to see if theve dried out to much. hope this helps.

peace

arthur