CFM fan for a cool tube

Looking to make a DIY bake around cool tube with either a 400w or 600w HPS. Most likely 400w for the time being with a 600w ballast.

Im going to have just the one light in a 4x2 tent but am wondering what sort of cfm fan I will need for the cool tube.

I plan to just suck air in from the one end of the cool tube and suck it out the tent. So sucking air from one end of the cool tube then through the tube then out through the ducting.

What CFM fan would I need to keep a 400w HPS cooled? I am reading all over and im seeing all sorts of different variations. Again im looking for just one fan for the one light.


Would a 6" 250cfm inline duct fan do the job?

if your tent is 4x2 a 250 cfm fan is sufficient

Hmm now the question is are the package options worth it?

Im looking to get a 600w ballast but a 400w light so that is kinda a prob with the pre constructed sets.

But looking at prices it looks like you can get a ballast/bulb/hood/socket set for around 200 before shipping.

What im looking at seperately are
Bulb ~25-30
Bake around - ~15
250 CFM inline fan for the cool tube ~ 35
Ballast ~ 150 (This is where I am hurting, are there no cheaper ballasts?)
As for a reflector it doesn't seem it should be a problem to make one or go without for the time being
Socket ~ pocket change at home depot

So really it seems all I need form the package is a bulb and ballast. So im not really sure if the full package is worth it/necessary.