For buckets with clay pebbles,
Fill the bucket with clay pebbles, using a pitcher slowly add water until it gets to your desired level taking note of how much water you added. This will give you a value that you can than multiply times the number of buckets needed.
Determining water level is more important when transplanting a new clone. If the roots don't reach the water level you must top feed for a few days.
Clones; roots from a water cloner are better than rockwool because they will grow long and when you transplant they will be in the wet zone. I am using rockwool for clones only because of the amout of clones needed.
I will take pictures later