Yeah, firefish and dwarf lion would not be a good combo, except for the lion. Firefish are good eatin' for a lion!! Decide which fish you want more. If you want the lion, you'll be pressed to put anything else in the tank simply because lions, even dwarfs, need alot of water. I have 2 volitans in a 150 gallon and I really think that they'll fill this tank up. If you want the firefish, you'll have more options to put other things in the tank. Have fun!!