Insulating tank cover

A tank and insulation system for covering a liquid in said tank, comprising

• a plurality of rectangular panels, with each panel having a top and bottom side, a first, second, third and fourth sides defining the perimeter of said top and bottom sides, said first, second, third and fourth sides having a locking rim which is spaced apart from said panel sides and defines a locking channel for engagement with said locking rim on adjacent panels;
• a plurality of circumferential panels, having an upper and lower side, an inside and outside edge, and a left and right edge, said inside edge being shorter than said outside edge so that said left edge and said right edge are not parallel to each other, said left and right edges having a locking rim spaced apart from said left and right side edges, said locking rims on said left and right side edges configured for engagement with said locking rims on adjacent circumferential panels;
• said plurality of rectangular panels configured to lock together when floating on a surface of a liquid, said plurality of rectangular panels creating a plurality of spaces defined by an edge of the tank, one of said sides of one rectangular panel and one of said sides of a second rectangular panel;
• said plurality of said circumferential panels configured to lock together to form a ring covering said plurality of spaces.