uhm! if your tank has plants and designs put frontosa, red peacock, venustus anything that has shinny blue coloration then use blue light, the light will show the greenest of your silver's scale, will make the fontosa's anal fins glow. be very careful with the size, get fronts that your aro wont be able to eat but not too big to bully your aro
if its a simple tank can get gars, snakehead, shovel nose, redtailed catfish, CK, oscars. size is always a factor never get something that will fit in their mouth, and get them together while their still young cause some of them could be very aggressive