well make sure u have god filtation
on my 55 i have 2 top filter it will help
silver dollars are cool -- i get a few
tetra are cool to thou i don't have much advise on them
cichlids -- are great mostly hardly
firemouth , ocsar , green terror , serviums,
snails are good to get to apple, mystery eat lots of stuff
don't get a iredesent shark will grow to big
my 55 i have a
green terror , small oscar, small sevrium and shark (its going go soon )
Prime example of what NOT to put in your tank, sadly.
An oscar alone needs 75g. Add the other fish and you're looking at about 125-150g.
In a 55g, a couple of angels (or other small/medium cichlids such as Rainbow Cichlids, Keyholes), a shoal of tetras (Columbian tetras are lovely, don't go for anything too small in ase they become angel food), some cories and a small species of plec (not a common plec). That would look lovely if you set it up in a natural looking way, planted, etc.
A Dwarf Cichlid community would look lovely in it too.