LionFish says......
Well, first off welcome to the board. Now, Volitan Lions are my favorite of all the lionfish species. Great choice. They are very hardy as long as they have been trained to eat already dead food such as frozen shrimp. Next, they are calm and as far as aggressive fish go, they are peaceful tankmates. However, you have a 55 gallon tank and it is too small to handle a Volitan lion. They get rather large (around a foot and two inches when mature) so I usually recommend nothing less than a 125 gallon tank. This is just my opinion but they need a lot of space to grow and a 55 gallon won't cut it for long. I recommend a Dwarf Lion, although they get 7 inches when mature they grow rather slow and they are as amiable as the rest. They have the same requirements as far as food and water conditions go. And remember, just in case you don't know, no small fish since they won't mind eating small tankmates. In a 55 gallon you could get away with a Snowflake eel, a Dwarf Lion, and a small puffer, just as suggestions. Hope this helps a bit.