The coralife 20w screw-in's aren't as bad as they're made out to be. My 2.5 ran on them for pretty much a year, many people have had good success with them (until they upgraded). Not exactly a metal halide, but they'll light a small reef pretty effectively.
Walmart sells a rubberized splashproof socket - wiring is pretty simple, white to white, black to black.
Andy
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