my arowana was about 8 inches when we got her, she's close to 12 inches now. She is comfortable in my 150 gal tank with her bestest buddy C. ocellaris pbass, 2 red bay snooks, the new TSN, and a couple big crayfish. And she'll go into the 240 when we get it set up. She will always be in the biggest tank we have.. and i say "she" because we named her Pinky, not because we actually know what sex she is.. lol.