After upgrading my lighting system from the standard T8 system that came with the tank to a two tube T5 overhead luminaire system. I decided to purchase this highly recommended T5 Powerchrome Aquaflora 39W along with the complimentary T5 Powerchrome Midday 39W. I have a pressurized co2 system and have been getting good results with my old T8 lights. Occasionally the odd pearling would take place. After installing these tubes to the luminaire. I was really impressed with the amount of light and the extra dimension they seemed to add to the tank. Everything seemed more real and lifelike as supposed to being one flat colour. The next day I arrived home from work to find every single plant pearling heavily. The fish seems more lively and their colours show more. Great buy and product!