Some of my lions are over 16yrs old now. I have a dwarf but he's a youngster at only 5yrs.
A 30gal would be a minimum in my opinion. They will eat right from your hand, however I recommend a food stick. Lions often compete in the wild, and since they are a bit slower they have a habit of a quick strike followed by a forward tilt. This places the poisonous spines in the defensive mode.
Never feed live fresh water foods, especially goldfish. They are nasty, hold no nutritional value, and can possibly carry a disease or two that can be transferred from fresh to salt water. (Most diseases/parasites can not transfer from one to the other) If the fish is picky and no other attempts to feed work a live Mollies is ok, but should be only as a last resort.
A varied diet of shrimp, krill, squid, and fish is a must for a lions long life. There metabolism is very slow. Feedings of say three times a week are sufficient. The will beg for more. Don't succumb to the beggars. As long as the fish is active and the belly is slightly protruded he is fat and happy. I have seen lions down right obese and stuck in a corner trying to digest. I once took a lion in after his keeper reported that his fish just sat in the corner and wouldn't eat. His diet was 5 large goldfish a day. The lion looked like a grapefruit, (Volitan) I kept him for a month before he was fed again, and trained to eat prepared foods. Charlie is now 14yrs with me. He is almost a foot long with amazing fins. He eats Mon-Wed-Fri.
One last note, if you bump your lion, dwarf or volitan, and receive a sting, rinse in the hottest water you can stand to take out the pain, AND there will be pain. I've been careless once or twice or the past 20yrs.
Good Luck
