I've nearly got all the parts to finally get my 20g up and going, but have still yet to pull the trigger on lighting. Either it's just out of budget, or someone on Craigslist snaps it up right before I do, and I lose out on a good and cost effective hood/light bar. However, I've been doing a little more research and have run into a couple of questions that I just can't seem to find answers to. As with most of my inquiries, I'm sure the answers are out there in plain sight...I just have knack for completely overlooking them in my search.

In all of my reading I've discovered planted tanks need anywhere between 1-5 (or more?) watts/gallon, depending on what you want to have planted. What I'm confused about is where that wattage is coming from? I was lucky enough to get a free light strip in a box of goodies off craigslist and the label on the back of the strip says 30 watts. That would seem to meet at least some lighting requirements on low light plants for a 20g. BUT, most of the 24" light strips I've been finding say 17 watts (or similar) on their labels.

Today at my LFS I saw all sorts of lights rated at 30+ watts. Now, this could seem like an idiotic question to some, but would those lights just not work in a light strip that is rated (or at least labeled on the back) at 17 watts? OR, so long as the light size (length and T-sizing) are the same, the wattage and K-value don't matter?

I'm all sorts of backwards on this one. And if you can make it through my rambling, then my hat is off to you. I just don't want to keep passing on light strips or hoods that would work.