Live Aquaria's tank sizes aren't completely right. They're a good general starting point, but they tend to be too small for many of the larger fish and they never list a fish as needing less than 30 gallons, even when that fish could live healthily in 10.
Volitans can reach sizes approaching 18" in diameter and here is Robert Fenner's comment on them and space:
Other than overfeeding with too much, too soon goldfish, this is the second deadly area where aquarists fail with their lions. Lionfishes, for all their apparent slow-moving, calm breathing, seemingly low metabolic lifestyles need space. Room to move, sites to hide/feel comfortable in, volume of water to provide adequate oxygen, dilution of their, at times, copious wastes.
Basically, they need about 40 gallons of space to themselves in a larger tank, so yes you could keep one in 50 gallons with no other fish, but I wouldn't count on it reaching full size or living to it's full age, because either there wouldn't be enough hiding spaces or it wouldn't actually have 40 gallons of useable space. Another of the main problems is that they generate a lot of waste that you have to clean up, because any cleaning critters in you tank are popcorn. The larger the tank, the less severe the problem is. The most common cause of death is actually overfeeding them, though.
With a hex, space is very different than a rectangle, so you should be able to keep the lion in a lower gallons hex, because the tank is going to provide room to turn around, which is why I'd never keep one in less than a 75-90 rectangle. They need a tank 2' wide as adults.
) and i was wondering could i keep a Volitan Lionfish and a Snowflake Eel. would the eel eat the lionfish or the lion eat the eel 
