Depends on what you are looking for. Are you looking for schools? If so large schools of harlequin rasboras are awesome. I have 30 in my 240 and they are super active and school tightly unlike some of the others. Also Roseline sharks which are also called denisons barbs or red line torpedo barbs are great and are a bit larger. Cories are a staple for my tanks and went a different route choosing to put 20 corydoras hasbrosas and have loved their activity level. They are a dwarf breed and only get to about 3/4 inch. Centerpiece you could go with GBR's or angels. Good luck.