Yep, he is eating PE mysis individually stuck on the end of a fishing line, and recently has been eating some slivers of other frozen foods (crayfish, shrimp) stuck on the end of the line. Biggest issue is that he looks at and and considers the food for several seconds before eating it, which gives the most aggressive eater in the tank, the Naso tang, time to try to swoop in a get the food first. I have had to separate the lion off with eggcrate in order to give him enough privacy to eat unmolested.

Depends on which lion you are looking at getting, the size of the tank, and what other fish you are looking to get. The easiest of the lot is the Pterois volitans, which is also the most common species you will see. It is also the one that grows to be the largest, and quicker than you would have imagined. You will see claims that it can be kept in a 75g tank, but that isn't really the case, not long term. While lions are fairly sedentary, they do need room to move when they do decide to move about, and a volitans would be best in a tank that is at least 24" wide.

The other fish you are planning on comes into it because if it can fit in the lion's mouth, it will likely get eaten at some point. Then there are some fish, particularly triggers and puffers, which will pick on lions, often to death.

So far the lion has not paid any attention to the goat, even when the goat is right in front of him. I feed the lion (and now the eel) once every three days, so he shouldn't be getting too hungry.