You can try wiggling the frozen shrimp at the top of the water so he senses the movement, then when it gets his attention, let it go. Or, put it in front of a powerhead and let it fly, lol. As long as it wiggle a little, it will seem live enough. I feed mine silversides, frozen. I just wiggle em by the tail in the water, and he loves em. Hes still kinda small, but growing fast. Also, my philosophy on Lions, is that they may get large, but they really dont swim around that much. So, I think they should be okay in a tank by your own judgement. Trust yer judgement, lol, cuz they realy DO just float around. K, good luck with the fish.