Trouble in the lion's den

From experience I concur with what everyone else said. I had a lion at one point. My 120g with a lot of rock was really too small, he was about 7 inches. Improper feeding, high waste and too small of a living space I contribute to the fish eventually getting sick and dying.

On a positive note, don't count the damsel out. Mine was smart enough to keep a minimum 6 inch perimeter from the lion at all times. They were in the tank together for about 8 months

 

FWIW/IME, the key to keeping an adult volitans is front-to-back depth...they really do best in a 24" tank so they can maneuver around. I wouldn't plan on keeping an adult in anything with a footprint smaller than 48" x 24" and a height of 20". That would be for a single specimen and a ground-hugger or two.