there was no water movement- i did notice that. you dont only need an aerator you need a filter. food that builds up after too much feeding will definitely kill your fish. there needs to be oxygen in the water and the untouched portions of food and the resulted waste needs to be sucked up and away from the fish. these filters have replaceable cartridges. once one gets dirty, after a couple weeks, you can put in a new one. hope this helps.
also, i agree with one flake of food. and once a day. if you really are worried about starving them, watch their bodies - the fat and muscle structure along the dorsal and belly areas. in my experience, a fish that is starving, in my case, it was ill and had no appetite, the back of the fish along the dorsal fin and belly start to recede. they were so hollow that i could see bones. but my fish was sick. and i doubt yours will ever come to this i would just advise to cut back the flakes to one a day - you only have eight juveniles and their tummies are only as big as one of their eyes.