A complete reactor media containing not only calcium and carbonate, but essential trace elements as well. In fact, A.R.M. has nearly 50 times the strontium of other brands. It is processed for immediate use with no rinsing required, has double the surface area of regular aragonite and features precision grading that allows for maximum carbon dioxide penetration. This coarse grade of ARMâ„¢ will prevent the clogging and upkeep associated with fine media and these reactors. The 1 gallon container has an average density of about 70 pounds per cubic foot.