Snails are slow and reproduce alot, they also produce alot of waste. You might not see it, but its there. Some plecos will eat algae, but lots won't. Plecos are true catfish and enjoy meaty foods as much as veggies. Most eat algae because thats what they get. As for otto cats they are small and are good for small tanks. Siamese algae eaters are like loaches and do eat alot of hair algae and try to scrape slime off the glass but leave trails due to their mouth shape. I like chinese and golden algae eaters. They have sucker mouths, love algae, and do a terrific job. However the chinese and golden algae eaters do get between 8 inches and a foot and get aggressive when large. I put 2-3 inch chinese algae eaters in my 80 gallon tank (the back of tank and plants were covered in algae). Two days later it was nearly spotless. Also rosie barbs are excellant for green hair algae.