The Marine section of this board is starting to get very restrictive these days. Anyone who dares challenge the general statements (filters are nitrate factories, all tanks must have 1kg LR per 2 gallons) is almost ostracised. Even the pinned guides (as linked by MW above) talk about a tank saying you want a long wide tank, rather than a tall one because of lighting. The assumption is made from the off that the tank will have some photo-dependant invertebrates in there.
I noticed that too, if you tell people that you are doing a FO nano/ normal size, they tell you your tank will fail with out LR, and its not just here, in other forums i got slated for it. So i set one up to show it can be done easily (and because i wanted marine fish), and people just go on my threads to slag me off. I also find that LR wouldn't be able to handle the boi load that a FO tank would make. The people here need to realise that there is not just one way to do things and they are also brainwashing new mariners into thinking the same. I have been told by very new marines (didnt know much) that my tank would fail because i didn' t a "life rock/moving rock/ that rock that filters you tank".
I researched for about a year and decided that i didnt want a reef tank i just wanted the fish so i just set up my FO tank. But im now hooked and am getting a much bigger tank. Will have no live anything, done the same way as my nano, mainly because i want a yellow tang

(them fish gonna cost me a £££)
This thread contains alot of information now anyway, so this can be your research start. And there isant a stocking rule for SW but the one that people say is 1 inch of fish per 5 gallons but no-one really uses that. Just keep your tank clean and you should be ok until you want to upgrade (dosnt have to be massive).
Good luck!