Very good thread; just wanted to add my two cents.
Of all the fauna listed to combat algae, I've kept nerites, ottos, amanos, mollies, and rcs. All do an admirable job cutting down algae, although IME mollies devour any leaves that aren't thick and hardy so I'll never keep them in a planted tank again.
Amanos are more expensive, but if you buy in bulk on aquabid they're about the same cost as rcs. They won't breed unless you add salt, but I've had the same group of them for 3+ years.
However, I've found that the best, cheapest and by far the easiest way to combat a large amount of algal growth is with the good ol' tag along snail (the species with a rounded shell, not the malaysian trumpet snail). They're free, breed at an exponential rate and they'll survive in the most abysmal water conditions. Yes, they attract widespread derision from most experienced hobbyists, but they're so functional. If they get too out of control, a yo-yo loach will make quick work of them. I must have had at least 200+ tag a longs in my first tank and one yo-yo got rid of them in 3 days.