Formula 28 Automatic Replenisher Formula 28 senses the concentration of 28 individual elements, including calcium, strontium, and all trace elements, then automatically adjusts each one to the same concentration found in the sea. The blocks or nuggets dissolve only to replace depleted elements in solution. Algae growth, bacterial filtration, and skimmers are all heavy users of trace elements. Sea-Lab's computer designed formula maintains natural seawater concentrations in spite of heavy usage, even in large Berlin type systems. Formula 28 also controls many causes of depressed or drifting pH. The formula contains four alumino-silicate "weathered" buffers, well known to seawater chemists, but exclusive to Sea-Lab in the saltwater aquarium industry.