It's possible, but long term success will take a lot of equipment, good husbandry, and a good amount of time. It's super frustrating when you can go to sleep and wake up to all your sps bleached or rtn'ed from a bad night.
Depending on your outlook it may or may not be worth the money and time.
Small tanks as you know are rough because of the swings... Temp, salinity, ph, cal, alk.. Especially involving sps. - all tanks are different so it's like a waiting game to see how your tank reacts.
I think choosing the tanks location is one of the most important things.. It will definitely help prevent most avoidable swings.
Depending on the location and if its open top or not you may or may not need A good heater, controller and
ATO..
I have noticed that the die hard nano guys make great reefers. Most of them don't know anything but a nano tank.
For people who own large tanks and then switch or try a nano I see a lot of bad habits and problems. Most give up.
Lighting is very important since u can easily burn or heat the water easily depending on what you choose.
I would also only go for aquacultered sps from people who have nanos - like myself who have daily swings for the best chances of getting hardy corals.
I would push you towards the 6+ range. I have seen plenty of softie/lps/sps fluval edges and tons of 10 gallons.
You could get away with picos by just going bare bottom and doing huge weekly feedings and 100% weekly changes from your main tanks Dt.
