You don't need a skimmer, water changes will do the job. Get fish that don't grow very large or need lots of room to swim. False percs, some gobies, etc. May have to do some research but those do well in smaller tanks. I bought live rock from PremiumAquatics.com and I recommend them but others like liveaquaria.com have very nice rock. I don't have a nano but what i've read is that the pumps put off a lot of heat which is not good in a nano. People use some of the smaller Maxijets like the 900 or similar which are more efficient, use less watts and put out less heat. Corals? I'd say zoos, shrooms and others that don't need lots of light. Just read through the site, you'll get some ideas as to what will work and what may not.