for quite a while, easily over a year, likely several years to life depending on factors that are based on the fish and your fish-keeping practices. a 6' long tank would be nice, but as long as you have it 2' wide the fish should be set for several years at the least--Aquaguy;2929991; said:hey, I have a 5.5'' florida in a 45gallon at the moment. I have an empty 120gallon(48x24x24) that I plan to move the gar into in a couple months. How long will might the 120 hold him. I understand its not easy to say.