With the modern filtration systems we are utilizing in our aquariums it has become more important to consider each of the key elements normally in NSW (Natural SeaWater). In order to keep stable and proper water conditions, the expert line additives are designed and formulated to provide the advanced aquarist the tools to individually maintain each of the key aquarium water parameters. Unlike most additives the Expert line additives are highly concentrated, packed in brown glass bottles and blended to give medium and long term results, rather than simply increasing levels in the short term. Typical Elos Expert line additives come in 25ml bottle and will treat approximately 3300 US gallons. Elos Expert line additives should be used by experienced aquarium keepers only. If you prefer the same quality ingredients in a easier/more forgiving form, consider the Elos Prima Line Additives.