If you're gonna use moisture retaining soil, I'd un-plant that baby into something smaller, like immediately. You are going to water that thing once, it's gonna weigh 120 lbs or more, and the water is going to lose its O2 (and your plant will drown in soggy soil) before it needs watering again. The roots can't get to all that water in their current form.

Fungus gnats will love that environment, too.

Sorry I didn't see this sooner. HTH, Hermie

I think a 400W HPS will handle that plant, as it looks at this point.