Well mine will have a fish in it on a temporary basis, but it evetually will be coral/inverts only.
Here's what I've got so far....
All-Glass Aquarium Mini-bow 5 (which despite the company's name is made of plastic
)
Hood has foil in it as a makeshift reflector.... working quite well
It comes with a 15w incandescant bulb and screw-in socket, which I have a 20w Coralife screw-in power compact in.... 50/50 daylight/actinic.
Heater is on order, a 50w visitherm
Filter is still a debate in my head, either the Fluval 204 I already have if I can throttle back the output to not create a whirlpool.... or an Aquaclear HOB filter. Currently running the filter that came with it with filter floss to get rid of all the dust from the substrate.
About 5lb of Florida Crushed Coral substrate
About 5lb of live rock
Total cost has been about $150 or so, but some stuff I'm using is what I already had, so I may be wrong on the prices. Aquarium itself was about $30, heater around $15, filter around $40, gravel $9, light bulb was about $13 when I bought it, I think..... and of course the expensive part, the live rock... $5/lb on sale for Christmas. I think the sale is because it was un-cured as I have now found out after filling the tank. In addition to that stuff you'll also need a hydrometer and synthetic salt mix, and access to Reverse Osmosis water.
As for the difficulty, that's yet to be determined really. Water topoff isn't as bad as my 20g because the little 20w screw-in PC bulb barely generates any heat at all. Trying to clean algae off may be a bit of a pain due to the curved glass of mine.... but in general, don't let people scare you off of nano-reef tanks by telling you what an absolute nightmare they are to maintain. My 20g requires a lot of stuff on a day to day basis.... top-off water, dosing calcium/alkalinity stuff, water tests, flake food for the damsels, pellet food for the gobies, scrape algae, etc..... but it's not difficult by any means. The beauty of saltwater tanks is that the live rock creates an almost self-maintaining system, in many ways.... nature in a box. The LR brings in the bacteria and hitchikers to help keep the nitrogen cycle going, and clean up detrius and such. Then you add hermit crabs and snails to take care of algae and stuff. And on top of that, if you're not doing fish.... the bioload is going to be amazingly small. Maintainance is essentially reduced to daily topoffs and feeding, with maybe a waterchange monthly..... rather than the weekly chore of water changes that you face with FW.
