How much gravel does a 55 gallon aquarium need?
It depends. If you are not using an undergravel filter, then 1.5-2 inches of gravel is sufficient. For a 55 gallon aquarium, 1.5-2 inches is 60-75 pounds of gravel. If you are using an undergravel filter, the recommended height is 2-4 inches (75-100 pounds of gravel). Also, it is best to use gravel that is 2-3 times the size of a pinhead. Do not, however, use fine sand in an aquarium that has an undergravel filter.
