You can kiss those coral bones goodbye because ever since a huge bust which seized countless tons of the stuff, the domestic supply of coral fingers has dwindled to nearly zero. One of the first and more prominent calcium reactor media in the US for years has been CaribSea’s aragonite reactor media. ARM has gone through several iterations in the past decade and now that coral fingers will no longer be available in the foreseeable future, Caribsea has gone ahead and sourced a new type of aragonite specifically for use in calcium reactors. The coral bones work really well because they are porous and their grading is coarse. The new ARM is also coarse and labelled as having a higher concentration of Magnesium than before, an element that could stand to be made available to reef aquarium in a calcium reactor, right alongside calcium and carbonate. We are concerned that with a lack of porosity this new media might not perform as well as the coral bones, and by performance we mean the ability to dissolve a certain amount of media in a given volume. This potential drawback may not be a problem for larger reactors but the little cute ones will likely need to scale back to using media with a much smaller grade.