Best kind of algae grazer for nano?

[asylumdown]

Is there any sort of a fish or snail that's a universal macro-algae eater that would be appropriate for a 20 gallon nano? My nano is currently home to a dwarf pygmy angel fish and a tail spot blenny, and while I barely feed at all (like one tiny pinch of crushed algae flakes a day), have a skimmer, and a hang on the back refugium with a rapidly growing ball of chaeto, there's this kind of macro algae that is just over-running my tank. I'm including a pic here. I took this right after spending an hour removing two weeks worth of growth, which when I started was so long and thick you couldn't see anything in the whole tank but the algae. When it grows out it develops an almost fuzzy like look to the tips of the plant, and is a gross greyish colour. It's on every rock that gets light. My nitrates and phosphates keep testing zero, which I assume is because they're being instantly consumed, but I have no idea where enough juice to grow that much plant is coming from.

Any ideas would be happily considered.