i have a 4X4X6 grow tent.. using a 400W HPS they are about 2 weeks old... it seems to be pretty hot in the tent.. I am getting a 4" inline with a carbon filter to take out the air... but do i also need to get something to push air into the tent? I have heard different things..one says yes you need an inline fan hooked to a HEPA filter bringing air in, and some say that you only need an exhaust fan like the carbon filter one and the air will come in through the intake whole on its own... someone explain or give some advice please.. I have 9 plants about 2 weeks old 3 look really good(in a mixture i made) and the other 6 are in frog something potting soil then they will go into foxfarm ocean forest mix.