How to know when to transplant?

3 weeks from seed and plan to move into 2 gallons for veg and then 5 gallons for flower. When should I move to 2 gallon?

Plenty of time

Depend on how long your going to veg. I would thro them into 3 gallons after they built a good root system. Hit them with great white shark and roots excell

When they get rootbound. Here is an article about it.

week 3.5 my self in same container abour to transplant next week

I transplant when roots grow outa the drain holes..