There is approximately 10 ml in 2 teaspoons - that is a tiny fraction of gallons.
If I did my math correctly I believe that you would need 150 teaspoons
3,072 teaspoons is four gallons.
51 US gallons is 39,168 teaspoons
1,248 US teaspoons = 1.625 US gallons.
500 US teaspoons = ~0.65 US gallons.
500,000,000 US gallons = 384,000,000,000 US teaspoons.
36 US gallons = 27,648 US teaspoons.
That is 2,112 teaspoons.
That is approximately 1,920 teaspoons.
1,200 teaspoons is equal to 25 US cups OR 1.5625 US gallons.
That is 76,800 teaspoons.