that is dedication.
good on you bro.
when i had one way back in the day, i fed it frozen smelt, from the supermarket.
i'd cut a few chunks and bury most of it under the sand. so that it could "hunt" like their natural behaviour.
i'd hand feed chunks of smelt too. but man, if they bite you, they got a good grip! it'd let me "pet" it too!
very cool animal. hope your efforts are rewarded and the stingray comes around.