Check the listing for details. Weco Wonder Shell | Super Size | For 10-15 Gallons. Condition: New. Listed at 9.98 USD. Weco Wonder Shell (Super Size) (10-15 Gallons)Weco Wonder Shells are great for pH, calcium and water hardness control in small aquariums and fish bowls. These all-in-one treatments provide calcium carbonate, sodium thiosulfate, and necessary trace elements, including magnesium Helps keep aquarium clear and maintains stable pH levelsAdds necessary minerals while removing chlorineGreat for goldfish, livebearers, cichlids and moreWeco Wonder Shells provide magnesium and calcium, which have been proven to help fish during stress and to prevent disease due to acid buildup in the body. These shells instantly remove chlorine and chloramines from tap water while also clearing cloudiness. Scour inner glass walls with a Wonder Shell to remove scum and deter its return