I know there's other threads along these lines but I'm just not finding answers to my question. The ballasts are going out in my T5 HO and I need a new light. Tank is a 48" 55 gallon. I'd say right now it's medium light, no CO2. I have Green Temples, Ambulia, Crypts, Blyxa, Balansae, Dwarf Sag, Italian Vals and a Red Melon Sword, all are doing great. It's roughly 18" from substrate to top of tank. So for a medium light replacement which one is better? I only want to use 1 light. Does anyone use only 1 of either lights on their 55 gallon? If so, how are the plants doing?