Fluorescent tubing grow

I'm actually growing NothernLights seeds under fluorescent tubes and was told that its at least 1 plant per 2 feet of tubing

if i grow under 48inch long tube can i grow 20 plants ?

i don't wanna come off sounding like a smart ass.. but.... reread your post... you say that it is recomended to use two feet of tube/ per plant.. and ask if you could grow 20 under a 48inch tube.. four feet.. that math in my book works out to two plants/ per four foot fube or/ 48 inches....
don't wanna sound mean, but i think your anwer is no, you can not grow 20 plants under a 4 foot tubie if t takes two foot of tube to support one plant..

my bad , didnt think before posting

.....and unless they're high output, they are not putting out very much light. (compared to a MH or MPS bulb) Before you think about increasing the number of plants, think about increasing the number or quality of the lights. Sure, you could put 20 seedlings under one tube. You might get 20 sorry looking stretched tall grasslike weeds, but you wont grow any desirable marijuana buds. You need a lot of light for healthy thick leave growth and likewise for buds.

With T12's (1.5" diameter), you need four - 4' fixtures (2 tubes per fixture) for a total of 8 lamps (tubes) to grow ONE big plant. That was my first grow. Even though I kept the lights as close to the plant as possible, the buds were not very dense (but full of beautiful thric's.)

Current (2nd) grow, I've switched to t8's, and will supplement those with a 75 watt hps during flowering. Again, for ONE plant.