Looking good Gerbilbox! ;-)
If you do go with some fish, I whole-heartily recommend a sixline wrasse. To this day it's a fish I've always had for the past 7 years of reefing. I once did not have any fish in my system, for about 4 months. My wife got fed up with no fish and told me I had to get some for her. As odd as this sounds, having fish makes reefing easier... they help keep the whole life cycle, plus since you have to feed them, their excrement is somewhat useful for soft corals. Looking forward to more!
I've got a 4" sand bed, I'm not sure how much is actually required, I'd guess that 2" would be enough. I know mine has at least 2 entrances I know of, about 8" apart and on opposite sides of my rock work. It tunneled under the edge of the rocks, and mounded sand up around the entrance. Have you read the article on them here at RA?
Jessy: Thanks! I would feel more comfortable reading up on it first. Reproduction and success of larva varies widely from species to species. I think it would be too much for my small tank to keep around a good-size starfish for the harlequin, as beautify as both of them are. The Pacific skunk cleaner shrimp is on my shortlist of invertebrates, as well as sexy shrimp. Alaska_Phil: I'm betting on little critters! I'm not ruling fish out, and a goby / pistol shrimp pair is really tempting. How much of a sandbed does a pistol shrimp need for its tunnels?
Cool! I always love to see nanos. I had a 20 long reef at home for a few years. Tiny tanks can be very facinating since you can forcus on all the little micro critters that evolve. I know you're not planning on fish, but I have to say my Yellow headed Antenna goby/candy cane pistol shrimp pair is my favorite thing to watch in my tank.
Nice plan! Though with inverts, I'm not so sure you have to worry as much about the environmental impact. I think they are much hardier and reproduce more readily than corals and fish. If you're going inverts, a nice pair of harlequin shrimp would be nice, but then you couldn't keep any starfish in the tank. I love cleaner shrimp as well.