have you read the basic starters guide? its as a sticky at the top of the marine page- its very good... Small tanks are harder to maintain. I would recommend a 150-200L tank for a beginner, not to big to require lots of expensive equipment and stock to fill and not to small that keeping water parameters stable. Marine tanks (tropical) are pretty easy to maintain as long as you are willing to spend the $ to get some decent equipment and are prepareed to read lots and spend a bit of time each week testing water parameters, dosing stuff etc... Check out othr tanks on here and elsewhere to get you started, and ask lots of questions...