+1 for Razorworm's comment. Otos are sensitive to water quality,if a tank is not fully cycled the ammonia, nitrites, and nitrates spikes could easily cause death. I don't add Otos to my tanks until I see diatoms or soft green flat algae types. If you are running out of food in you 10 gallon try Hikari Algae Wafers or blanched zuchini or cucumber.
75 Gallon, 2X55W AH Supply CF 8800K, 1XMarineland Doublebright, 2X Marineland 350 Magnum; 45 Gallon Tall, 96Watt AH Supply CF 6700K; 30 Gallon Long; 2X36W AH Supply CF 6700K; 20 Gallon, 1X26W AH Supply LED kit; all with Press. CO2; (Calcined) Montmorillonite Clay
Greater Seattle Aquarium Society (GSAS)