Otocinclus and diatoms on tiny leaves

Do Oto's eat diatoms off dwarf baby tears? or HM? I have only have one oto is a 29 gallon tank and so far he only stays of the sides of the tank and occasionally he is on my dwarf sag. If i get another one do you think he'll get it off the plants? I also have amno shrimp but they don't seem to eat any off the leaves.

Yeah i want to get more but the store i got them from only had one. how many do you think i should get for a 29 gallon? also will they be a problem with a breeding pair of apistogramma cacatoides?