If you use calcium and magnesium to supplement your aquarium, do you really know what you're putting in your tank? Without testing, you may think that all supplements are created equal - but unfortunately that's not the case. There are multiple sources to produce these minerals including mining, evaporated seawater and synthetically processed. Mined and evaporated salts almost always contain a variety of contaminants and organics from the ground, water and air - even machinery. Often times these are designated as "technical grade" and used for industrial applications like ice melt. Synthetically processed materials are more common in pharmaceutical or other industries where ultra pure material is a requirement. High quality salt for these industries typically has extremely low impurities, organic and insolubles. How can you find out which material your favorite brand is using? Well, generally if a brand is using a synthetically processed or pharmaceutical grade material it will be advertised on the package. If it isn't, it's almost certainly a tech grade material. You can check for quality with a simple visual test using some RO/DI water, your preferred brand of additive and a martini glass. You might be surprised with what you find! Connect with us on Facebook: http://www.facebook.com/BulkReefSupply Check out our pics on Instagram: http://instagram.com/bulkreefsupply