How many gallons of seawater will be displaced when 200 pounds of live rock is submerged into a 135 gallon reef tank?

To determine how many gallons of seawater will be displaced when 200 pounds of live rock is submerged, you would first need to know the rock's density. Generally, live rock has a density of about 0.5 to 0.8 grams per cubic centimeter. Assuming an average density of 0.6 g/cm³, 200 pounds (approximately 90.7 kg) of live rock would displace about 30 gallons of water. Therefore, when submerged, around 30 gallons of seawater will be displaced from the 135-gallon reef tank.