The algae that grows on the scrubber isn't "special" or superconcentrated. If you have fish that like/need veggies (like tangs or foxfaces), algae is an important part of their diet. Obviously, feeding them the algae will recycle some of the exported nutrients back in the system, but no more than feeding them algae foods from an external source.
Personally, though, I wouldn't give them hair algae off of it, just because it's a lot messier to feed them with. A lot of it will get scattered and stay in the tank. Caluerpa is easier, because it's big pieces that don't really break apart.