This summer I am going to have a small container pond that I will put out on my patio. I am really wanting to get some goldfish ( probably the small feeder goldfish) to put into it, but I don't know how much I should get. I want them to live a long lasting life and be happy I am also going to get some water plants to put into the pond. The pot is 17 inches tall, and 21 inches wide. Thanks in advance!