Must be something about your water the Oto's like . Like Madagascar said, you don't hear of them spawning in home aquariums very often.
I think they like the twice a week 50% pwc's! They also seem to love my amazon sword, gets a bit of algae on the leaves and they basically hang out in there most of the time, the only time i see the adults out and about is at night after lights off.
There are quite a few photos and videos online of people successfully breeding otos - you seem to be one of the chosen ones! Congratulations.
Thanks firefly! I actually started thinking about setting up a tank just for the otos to see if they would breed again in a safer environment for the fry. If I can just sneak another tank past my husband