snails will eat algae but also produce a lot of waste....otos really are the best bet for a small aquarium...i have 4 in my 10 gallon planted and the only time they dart around like that is when the lights are turned on when they aren't expecting it...the high mortality rates with otos has to do with buying ones that aren't healthy (usually have slightly sunken stomachs and lack the bacteria that break down food in their stomach for them, so have problems with digestion - i believe that's what i've read at least)...assuming you buy one that doesn't have a sunken stomach and supplement their diet with algae wafers a small school should live just fine in a 10g - they are the most suited of any algae eater