these are all great starter fish and maybe you could do a small clownfish or some peppermint shrimp SteveO said:Dont bother. Too small for a newbie. Stay fresh until you can do a 50G or larger for salt. Simply the equipment cost for a salt, I could imagine would be more than you would want to spend. After an RO/DI unit, live rock, sand, skimmer, salt, reliable test kits (Mott, Salifert), and whatever small bits and pieces you would want to have; you'll probably have around $500 invested for a 15G.
The 20G above needs more sand and rock... as well as skimmer.
. try it and if you see it costs too much for your budget go back to freshwater and wait till you have some to get a larger tank. What ever you do...GOODLUCK