depends on the size of the tank as well as the type of puffer, the one in your specs is not big enough,
what its been fed before also plays a large role. most if not all will eventually snack on the lions fins, and if they decide its food, well dead lion and or stung puffer.
unless you have a very large system that can handle 2 18" fish (guesstimating on the puffer size, other than the tobies which get 6" but who love to fin nip) you will probably run into issues.