LionFish says......
Well, to be completely truthful with you, that book should be burnt. However, maybe it is useful for other info but it certainly should have more than a 20 gallon tank and it gets to be at least 6 inches if not more in time. 20 gallons, huh? Well, I recommend nothing less than a 55 gallon tank for good room to grow. Also, as far as lions go, it seems to be one of the least hardy lions. It usually is pretty hardy but it doesn't mean that it is easy to care for. It needs more attention paid to it and the water quality should be excellent to provide the needs for it to thrive.