you can use tongs and hold krill by the tail and just wave it to catch its attention DO NOT SHOVE IT IN ITS FACE or try and force it to eat that will just make it loose interest , because in the wild the fish dont just come into its mouth, remember lions are hunters , half the fun is the hunt , make it look distressed because they are also opportunistic
also another way is get a piece of krill and with your hand just wave it just under the water surface to catch its attention and slowly move the krill across the water
during all this regardless of what way you choose , keep an eye on your lions eyes , if its interested it will follow the food with its eyes, its not easy and it is irritating at times but well worth it at the end. it took me 10 days to get mine to eat , and it was because he was starving, during the training process DO NOT DO NOT feed it live food or youll be back at square one, you could probably entice it to eat by soaking the krill in garlic extract
hope this helps