having some experience keeping FW
fish does give you some advantages over a complete fish keeping newbie. For instance, you are already experienced with tanks, filters, and possibly sumps or wet/dry. You should understand the nitrogen cycle. You should have some experience performing water tests. Just remember that many things with SW
are different. For example, your main filtration in a reef tank is just live rock(1 to 1.5 lbs per gallon) and a DSB
(Deep Sand Bed) of 4" - 6". The only other mechanical device used in todays reef tanks are a protein skimmer.
I would not say that you "need to keep FW
fish" far any certain period of time. I just think have some(not a lot) FW
experience will help.