Hi Matt, I believe with the Catalina you actually have 2 each 2X54 watt circuits. A lot of people will run one circuit for the full period and do a "noon burst" for a few hours for the second circuit to maximize plant growth and still keep algae growth under control (LOL). Roy _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member