Why a tent
A grow tent does four useful things at once. It reflects light back onto the plant, blocks light from leaking out (which matters during flower), gives you a sealed volume to control the climate, and provides bars to hang a light and fan. Growing without one is possible, but a tent makes the rest simpler.
Sizing it to your plants
Choose the size from how many plants you want and how large they'll get, rather than the reverse. A photoperiod plant in a 5-gallon pot takes up roughly a 2×2 footprint by flower.
- 2×2 (about 4 sq ft): 1 plant
- 2×4 (about 8 sq ft): 1 to 2 plants
- 4×4 (about 16 sq ft): 4 plants
- Leave headroom. Plants can roughly double in height during early flower, often called the stretch.
Setting it up
Mount the light to the top bars on adjustable ratchet hangers so you can raise it as the plants grow. Place the inline fan high in the tent (heat rises) pulling air out through a carbon filter, with a passive intake low down. Clip a small fan to a pole for canopy airflow, aimed just over the tops rather than directly at the plants.
Light leaking in during the dark period of flower can stress plants into producing seeds. If you can see light escaping the tent with the room dark, seal it with tape.