do u need a fan if u have co2 going?????

from what i reasoned your really only needed the fan to mave air ....but if u dont need to move air cause u have direct co2 being put on the plants do u really need the fan?? now i susposed mabey to help stregthen the plant ok so mabey run it 6 hours in 24????and kind of an off topic question im growing 2 tomatoes and a cucumber under the same lights as my plants and there about 2 weeks behind..should i put them under different light when i begin 12/12??or wil they be fine under the 12/12 the tomatoes and cucumber are only 1.5+- weeks old?

What kind of cucumber? I'd love to grow some cucumbers, but in my outdoor growing experience with them they take up a large amount of ground.

yes...you still want to keep the air circulating so hot spots and stale air pockets dont occur..

You need constent airflow even with co2. recomend turning the airflow off when using co2 cause u want ur room to be as saturated with co2 as possible

ok that answers one of my questions ty what about the rest???

i wouldnt have a fan with co2 running. i would use co2 at night during lights out and you wont need a fan because of heat. make sure your bottom of your grow room is air tight cuzz co2 is heavy gas that stays low

who knows about cucumbers and tomatoes

ok ty again with the c02 queastion....what about and kind of an off topic question im growing 2 tomatoes and a cucumber under the same lights as my plants and there about 2 weeks behind..should i put them under different light when i begin 12/12??or wil they be fine under the 12/12 the tomatoes and cucumber are only 1.5+- weeks old?

Just like any plant if you want it to continue to grow then it will need longer light but if you want it to bloom then you would shorten the light cycle. I don't think that they will be ready to start blooming as soon as you want you babies to.