@gjbarord
I am remiss on taking some video, partially because I want to try to document learning that I am still not totally sure exists. Last night, however, encourages my thinking. Nemo seems to have become accustomed to being fed when the lights come ON (ie seemingly opposite night feeding). He appears to recognize that I bring food at this time.
Last night we were late coming home and I was planning on a fasting night (I am not very good about fasting one night a week - something I used to do). Normally, I feed the other critters in the tank with a shrimp slurry to stimulate a feeding response (very effective) but last night the queue seemed to be seeing me moving about the kitchen. Nemo is in the dining room, visible to the kitchen but about 20' away. His lights were cycling back down to off and he was "sleeping" until he saw me then he started swimming with tentacles extended (hunting). I thawed him a piece of salmon, walked to the tank, showed him the food from outside the tank and he came up to feeding depth (within a foot of the top - tank is 3' deep) and over to my hand to accept the food without dallying. This is the first time I was fully aware (but have "thought" he was responding this way) that he is understanding a feeding routine.
I also "think" he tells me when he wants a second piece of food. This is a little harder to confirm/demonstrate or be sure of what I am watching (and more fascinating). I only see the behavior about once a week and am not sure how to demonstrate/record it convincingly.
Lastly, I am convinced that food size is important. I have found this to be true with octopuses when initially trying to get them to eat dead food in an aquarium and my "eye sized" proportion seems to fit optimal sizing. Unlike octopuses, Nemo does not typically reject a piece of food too large but will only eat a portion with the remaining dropped to the bottom. Occasionally, if he was still hungry, he would locate the dropped portion and eat more but not necessarily all. Since I have reduced the portion size, he eats the entire piece daily.
I mentioned an observation with Zilch that you had not observed but I have seen it with Nemo as well. If the food is too large or has been accepted and then rejected (rare or not at all since changing the food size), it appears it can be difficult to free it from his tentacles. He will work hard to blow it away with his siphon as if he cannot release it with tentacles alone. I don't see this since I have made the food smaller but may try to offer an over-sized portion and try to video the behavior.