I have been utilizing a very dynamic feeding schedule with a diverse array of foods.
I never feed the same amount to each ray, nor the same food. I also will "fast" one or more of them for half a day to 1.5 days then feed generously. I try my best to partially mimic the feest and famine found in the wilds.
I rotate daily, weekly, monthly between frozen, farm raised shrimp, nightcrawlers, smelt, krill and a very specialized customized, commercial trout chow. Actually I have not been able to see the ingredients, percentages etc. All I know is that I showed my PHD Aquacultrue friend a bag of Hakari Massivore and three days later he produced eight pounds of this pellitized chow.
A little amateur science here:
I have noticed that since the introduction of frozen shrimp and this "chow" the barbs shed by the rays are much, much more dense and firm. Previous to these foods the barbs were rather flimsy and easily bent. They also tended to be kinda malformed ex: blunted, serrations absent.
Now they are a force to behold.
Respectfully,
FireMedic.
P.S: I will get the low-down on this chow and post it.