Honestly, I just want my fish not freak out when I turn on the light. The current light in my Eclipse is so bright, that my fish scatter and hide when I turn on the light, granted they come out later, but they can't like having a bright light suddenly turned on. I've also heard that fish do "better" under dawn and dusk simulations. Basically, I want to have the best tank I can for my fish without breaking the bank. Second, The eclipse twelve has that odd shape to it, so it is hard to fit normal bulbs into the space left. Third, I've heard of bulbs that get progressively brighter, and then when shut off dim down slowly, I thought these would work, too, just trying to get a feel of what works best.