For the richest stock the water level should barely cover the bones. You can always dilute it later when making soup.
The heat should be low enough that the water doesn't deplete. I usually see a very faint bubbling when I check on it. My stockpot lid has a tiny ventilation hole so during the 48-hour batches I might add 4-8 oz of water if it falls below the bones but usually not.
Lots of: urban hiking, cycling, sprinting
Lots of: fresh meat, seafood, eggs, organs, tubers, starch fruits, vegetables, meat fat, dairy fat, oil fruits
Some: cured meat, dairy protein, sweet fruits, rice, pulses, tree nuts, oil seeds
Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, refined oils, peanuts