20L way too small mate.. if you want a small tank for fish go for 150L or so... Couple of clowns and a small goby... One thing you have to remember is that unlike freshwater fish, most gobies are wild caught... So although you have a certain responibility to care for freshwater fish as they are live animals, this responsibility is amplified with marine fish as they are caught in extremely fragile ecosystems. Because of this, it is PIVOTAL that you do alot of research BEFORE you get into it... Ask questions for sure, but do lots of reading first... Chimera has put a selection of links at the top of the page, there is another NZ site for marines so check that out. Also check out Reefcentral, Reefs.org, Advanced aquarist mag (read the archives too), Reefkeeping mag, Ozreef etc... Rant over...