I believe it is 4 liters to a gallon, so those would be 5 gallon pots..that seems undersized. I used to use 600 watt bulbs and I did 4 x 3 gallon pots (12 liter?), and then I switched to 1000s and started using 4 x 5 gallon pots. So that equation would be 2 gallon (8 liter) per 100 watts.
I...