For clams halides is the way to go. With halides you will get great penitration which the floresents lack. T5's are great but they cant penitrate deep down to keep the max's and croacias on the sand bed, i would go with a 250 preferably the Double end set up....but single end 250's would do a great job as well, you just get more par out of the double ends....400's are Great but give off more heat and burn more energy....but in the end its all in what you want to keep what your preferences are....