I love these stories of huge cichlids, bigger than people have seen in their lives, yet no pics. A 5 ft long 18 inch wide tank would comfortably house a solo Jag of 15-16 inches. Past that, an upgrade to a 180 might be in order. That being said, in my 23 years in the hobby I have rarely seen male jags get over 16 inches. I have seen it, but is rare even when kept as solo fish in large tanks.