I have a 55 g tank as well and I have a 4 bulb T5
HO set up with 8 moonlight LEDS it was like 102 shipped off e-bay and it works really well. Ive had it for a couple months so far and every coral is thriving in my tank. I have some zoas, frogspawn, torch, hammer, candy cane corals, bubble coral, purple sea whip and some others cant really remember.