Algae on the light tubes is a Bad Thing, as temp said. That means your lights are exposed to water, which you really should fix.
And, if the algae you're talking about happens to be distinct, non-furry green "dots" that are very difficult to remove, then it's probably what's called "green spot algae". If this isn't the stuff, ignore the rest of this post.
If so, then I'd add this, from my own experience:
* I don't think any fish or snails will eat it.
* I usually see this kind of algae in newer tanks (within the first 2-4 months after cycling). Most of it usually goes away eventually; at least the stuff on the glass doesn't come back after scraping -- the spots on older plant leaves are there to stay without intervention.
* When it starts to "go away", that's the time to keep an eagle eye out for other forms of algae starting to develop. It's almost as if the green spot algae is the "first green algae in the algae cycle of a new tank".