As recommended I would repost in general salt. I am one of the more active salt members, and almost NEVER come into this area.
That being said, a 20g L is a decent salt tank, but larger is usually recommended for novices. I think that you can do it anyways, as long as you do your homework, and have some friendly MFK people to help you.
Your stocking list also looks good to me.
Some advice? READ! Books are better than the internet. Fact. Best source of info on the internet in my mind is wetwebmedia. Do a google search for them. Forums are good, but WWM has a huge source of troubleshooting essentially on almost everything in the hobby.
Filtration is big, with a tank this size sumping might seem "awkward", but its the recommended form of filtration for SW tanks.
I also recommend the use of protein skimmers, especially AquaC brand.
Really if you want more help, just post more specific questions!
