Sand and rocks are virtually essential for any marine aquarium. While their implementation various drastically from hobbyist to hobbyist, they serve as the base for any marine tank, and the foundation of a sound system of biological filtration. Despite their immense importance, however, they aren’t without their drawbacks. Even before you put either into an aquarium, they present enormous challenges for hobbyists. If the sand and rocks are live, meaning pulled right out of the ocean, then they are loaded up with all sorts of sea life that is likely dying from shipping stresses. On the opposite end of the spectrum you have the dry, dead stuff. Unfortunately, it is also full of problems. Besides being devoid of all of the beneficial life, it is also full of phosphate, which ultimately leaches back into the aquarium over time, causing problems long term. So, either way you look at it, there are issues to be had, but they are avoidable. Curing live rock and sand is one of those ways, and soaking dry rock in freshwater for an extended period of time while running phosphate absorbers is another.