No, i believe not.
The length of the bulb is dictated by the wattage.
T8 30W bulbs are 36"
T8 18W are 24"
My 2 foot tank has a lighting unit that houses 2 X 15W T8 (the bulbs don't span the entire length)
Its just i was given an arcadia 30w light unit and thought i could use it for my 2 foot. Ill sell it off and buy a smaller setting.
i want to acheive about 2 wpg so not sure what i should get. maybe T5 instead along with C02. I know its a guess to what lighting as WPG is hit and miss. Two 15w T8 will give me 1.6 wpg for 70L tank.