Perfect to make caves in Fresh water aquariums.

This lava rock will need to rinsed before putting in the aquarium. 

Most rocks are in the 1-2 inch range

Perfect to make caves in your fish tank. Use this link for Aquarium safe silicone to glue the rocks together.Aquarium Silicone 

Of course wash them, put them out in the sun light for a day to dry before you silicone them together. 

Wait two days for them to dry good before they are siliconed.