Try and stay with 3 or 4 main species (totaly my opinion). Resist the urge to buy one or two of everything (I know it's tough). Look at your tank in sections (upper, mid-level, lower-level) My personal favorite for the upper level (simply because they actually stay there) are hatchet fish. One or two schools of tetras will be good midwater residents. Standard bottom dwellers are a school of cory cats. Throw in some otos for algea control (dwarf species of pleco would work too). Now you can choose your "center piece" fish. Something that gets a little larger and garners most of the attention. Your on your own with that one, but a south american cichlid with a more peaceful reputation would be my choice. Again, this is totaly the opinion of someone who themselves has already suffered through the "Frankenstien" tank phase. An alternative would be a tank full of Rift-Lake "African" cichlids. It would result in a bit more boisterous tank, but is worth looking into. Good Luck.