I have a chance to build a SW tank (I'm not really a marine person), and it's been a while. I have a cousin the FL Keys who likes to snorkel and has offered to collect and mail me some plants - from what I've read most macroalgaes can live for 4-5 days during shipping. Once the tank is going, I'm going to drive down and do some collecting.
This is based on my previous Bathroom Tank: 10gal, filtration is a HOB filter with no media, but the intake is covered by a seafan skeleton completely covered with Caulerpa. One 15watt 10,000K bulb. Live sand, chunk of live rock, barnacle skeleton and aragonite sand. Denizens: two hermit crabs, a brittle star and a mated pair of blue damsels (Mr. and Mrs. Bathroom Fish) - the male, I think, set up his krib in the barnacles and spent his life tried to coax his mate into them - for all I know they spawned all the time. Care - top off with well water, nothing else. Water quality - perfect and utterly stable.
Bathroom Tank 2.0 proposed setup: 20gal tank, lighting - 2x15watt 6500K, lighting - fixture from 10gal tank with two sockets for incandescent bulbs, filled by 30watt CFL, (I'd like to simplify this later). Circulation: Sunsun wavemaker JVP-110 (note, if you look, you can find a deal on these - 4 for $25), substrate - aragonite, collected live sand, 1/3 of the tank is behind a rock barrier and deeper, 3" with mud underneath.
Stock - Seagrass - Halophilia engelmanni, whatever else I collect, - Caulerpa mexicana, Chaaetomorphia, Halimeda, Penicillus, Botryocladia, Halimenia floridininsis, Padina, Gorgonians - Briareum, Plexaurella, Brittlestar
Fish possibilites: royal gramma, chromis limbata, cocoa damselfish, cherub angelfish. I'd like to have at least two fish...not sure which would work.