Tiger Barbs can be nippy if not kept in groups of 6 or more. More often than not they get themselves killed. Giant Danios are a good option, but are very skilled escape artists so keep the tank well covered. Tinfoil Barbs get quite large and do best in groups of at least four. So unless you have a very large tank I'd skip this one. Silver Dollars are another option just a little slow moving. So often times will show alot of abuse(nipped fins). Finally my favorite dither is the Beunos Aires Tetra. While they can be a bit nippy they aren't as bad as Tiger Barbs plus they are a quick fish.