About the sand moving...usually it will start to develop a bio-film throughout it and become more stationary as time goes on. Also as mentioned before, 18lbs of rock isn't going to provide a lot of filtration. If you like the minimal rockscape look you can always add a sump with a bunch of extra rock. If not then you could greatly benefit by adding rock to the display. At this point you already have live rock and I would highly recommend using dry rock for the remainder. Its less expensive and in a few weeks it will work just as well and in a few months it will look the same too. Marco Rocks sell good quality dry rock if you are looking for it. Coral can be added as soon as the tank is cycled(ammonia 0, nititrites 0), but as others mentioned you may not want to add any of the more demanding corals until you have a good handle on water chemistry and how to keep it stable. A good starting place is always your softies such as mushrooms, zoas, xenia, leathers, and some LPS (large stony polyps). Hopefully getting into the hobby you do a lot of research as this will definitely make things go smoother, saving you money and heartache in the long run. Not sure if you are running a skimmer, but for that size tank I would highly recommend one or if you prefer you could use alternative means (do some research). the number one piece of advice I can offer is to use good water. This mean RO/DI water or its equivalent. If you can't spring for the purchase of an RO/DI system yet ($130 or less for a used one) you can usually get water from a LFS or you can get distilled drinking water from grocery stores (usually most expensive). Using tap water with conditioners or without is a sure way to lead to some common beginner issues so definitely look into your best options for getting good quality. Welcome to R2R and happy reefing!
