The only dumb question is the one not asked...
No, algae wafers won't promote algae growth. The algae cells are dead from being dehydrated.
As for growing the algae, the easiest way I've seen it to put a tank out in direct sunlight w/ water and whatever rocks you want to grow it on. Give it a couple months and watch nature do it's job. They will "appear" out of nowhere.
There are also a few mosses that grow in this fashion, so I want to make sure that you're referring to algae and not to moss.
I have a piece of driftwood that has some dark algae growing across it in a layer. There are a few java ferns growing on it too. It looks nice.
I'm sure there are others out there with more expertise in this area that I have, so wait for a few more responses to see what they have to say
