Place flasks eight to 12 inches below the Gro-Lux tubes; keep on for 18 to 20 hours daily. A70-725
The amount of Gro-Lux lighting necessary can be determined from the fact that one four-foot tube running across half-pint bottles will cover an area fifteen inches wide and four feet long; use reflection to reflect side wall light; cover with aluminium foil. A70-427