Well, 500 watts of metal halide is WAY too much for a 55. They will raise your temp a LOT. A nice LED
panel, equivilent to a 250 watt 14k bulb can be had for between 300 and 400. WAY cheaper then 600 and a LOT less electricity and heat. Then supplement it with a dual strip 78 watt T5. One 39 watt actinic and 1 39 watt 14k. Great lighting system put together for about 550. No heat, little electricity. My LF has a beautiful LED
panel with cooling fans and the works for 300 and has them over his coral tanks and they are awesome. I have a 200 gallon with 3 halides. One at a time I'm going to replace the halides with these.