what size duct booster fan for my tent?

Hello everyone. I have a small 32x18x32 with a 2ft x4bulb T5 light for starting seeds and start of vegging. I was wanting to what size duct booster fan should I use for pulling heat if any from the T5 light. Should I use a 4inch fan that is 100cfm or the 6inch fan that is 240cfm? I was thinking the 6inch might be too much.

Get a 6 inch with a fan speed controller. That way you wont have to upgrade in the future!