Ottos-don't know anything much, is said to be intolerant of travel stree, small.
Sae-is too big for small tanks, but is a great all around algae eater otherwise. eats the dreaded black brush/beard algae that no/few fish would touch. Entertaining to watch, too.
Cae-has a bad rap, since its not really a good algae eater, especially when it gets older. It will suck on the fish slime instead. Is a good fish IMO, but not for the purpose of controlling algae. Can become territorial/aggresive.
Algae eating shark- I have one, although its a red tailed black shark. I dont know if it will stop eating algae when it grows older, but it is now. I do have SAEs, so no problem there. Eats most algae.