Giesemann Tropic 39W 36" T5 HO Lamp 34 inches from end of pin to end of pin (for 36 inch fixtures/retrofits) The Giesemann Tropic is a full spectrum 6500k HO T5 lamp with enhanced photosynthetic peaks which recreates a natural sunlight effect 39W T5 HO Lamp. Will work in any T5 fixture, as long as you are using bulbs of the same wattage and length as those currently in your fixture Recommended for freshwater & marine fish only tanks The specially designed light spectrum inhibits algae