A 30 watt T8 would be perfect for cloning or starting seedlings but anything more than that and you will end up with very tall skinny plants with barely any branch tips. Less branch tips = less bud sites. If you absolutely must use that light, make sure to keep it about 1-2 inches from the tops of your plants. When I used to use them for vegging back in the day, I would damn near touch them to the plant tips. For clones and seedlings you would want to keep them a litte further away. Maybe 6-12 inches.