Large fish for a 55 gal? Single or small group?

Goldfish! Three beautiful goldfish can get very large, and a 55 gallon tank would be perfect! You may think that goldfish are "common and not exciting" and you may be right about the common part, but goldfish are extremly smart. They remember things very well, and can actually be trained to do things! So a trio of these amazing little (large) guys would be perfect for your tank :)