"Long" tanks almost always mean low tanks, so you can't use T5HO light without hanging it high above the tank, and T5NO light is also a bit too much. But, you can get lots of light with T8 light strips. How high is the tank?
24 x 8 x 12 should mean the tank is 12 inches high. If so, two T8 bulbs would give you good low light, maybe low medium light. Another good option is a Hagen Glo single bulb T5HO fixture, on the legs that come with it. That would give you high light.