your fixture just doesnt have the intensity to successfully support corals regardless of the type of bulbs you have. now when you do upgrade either to power compacts, metal halides, vho, or t-5 flourescent, you will want to have a combination of daylight 10k bulbs and actinic blue bulbs. all reef floureescent fixtures(pc's vho t-5) will come with both types of bulbs or bulbs that are 50/50. mh's may not need actinic depending on what k bulbs you get. mh's are the best and most expensive. ime ther is little difference in flourescent fixtures that are of equal power.