I went similar route as you took. I did not use the metal halides lamps however. I just stuck to a bunch of florescents available at the time for reef oriented tanks. I had a 55gal as well. I built my own filter systems using the spinning arms, and rolls of filter in large rubber buckets with loosely fitting lids. System got destroyed after maintaining it for about four years. Left the house for a weekend of work with a small computer firm, returned into my drive way wondering why the Colorado river was pouring down my drive way. Toilet went bad just after I left on a Friday... half the house got destroyed by water damage including the reef system on the first floor living room. Lost a few thousand on that deal.
But it was an enjoyable hobby while it lasted.
I remember rigging a bottle with purified water, Iodine and something mix. It made the coraline algae go nuts. About that time a Prayer got answered about moving but the aquarium wouldn't make it.
Gave back the setup and corals back to our favorite Hobby shop where they were sold to others. Green Mushrooms by the boat load, hermit crabs and small fishes and rocks that gave all those strange creatures. Yeah, I miss the reef.
Have fresh water now with plants and go to the sea whenever I can. Once it gets into you it never lets go.
SR