Nanos can definately be done but as i said to you Dixon i think it helps if you have quite a bit of experience with marine tanks in general. This gives you the background knowledge to know whats "going on in a tank"
I have an 8 litre pico which has been up and running for the best part of a year and i find it rather easy to maintain and very enjoyable.
I think it is important to realise the limitations of a nano, in terms of what you can keep and what the system will handle. I imagine if you had no background it may be very easy to overfeed or get bad coral combinations, fiddle too much etc, that sort of thing
Things can definately go bad quickly if you are not watching things closely. In saying that i have not found it any less stable than a larger tank because the bioload is in proportion to the size of the tank. The only thing receiving direct food is one sun coral polyp. The only tricky parameter i have found is temperature. When i had it in a hotter spot it definately wasnt happy. Now i have a good spot it is doing great.
All my corals are second or third generation frags so they are hardier than wild corals. Currently i have Green Star polyps, Candy Cane, Rhodactis and Discosoma Mushrooms, Zooanthids, Torch Coral, Xenia, Yellow Sarcophyton, Blue Turbinaria,Yellow Sun Coral, Yellow Polyps,Orange Monti Cap and Some Blue Tip Acropora.
The Tank has a Hush 5 Power filter running Seachem Seagel, a 9w Pc Blue/White bulb and a elite mini heater.
I do a 50 % water change every fortnight and feed the tank 1 drop of JBL Koral Fluid every day and feed the suncoral a couple of brineshrimp 3 times a week. The seagel is changed every month. Thats all i do for maintenance.
I think another point worth adding is this is the only tank i have to look after( with the exception of the shop) so it gets my undivided attention at home. Also i am happy with what it can keep and dont want to try pushing it with too much livestock etc. If i was starting with marine i think there maybe a tendancy to want to keep more corals, fish etc and you may not be happy with a small tanks limitations.
Ok i have waffled on a bit more than i planned, just wanted to get my experiences with my pico tank across.
Kind Regards John