[leahski]

it just seems like it would be such a sad, aweful life for a shark or ray or moray in a tank even that large. its one thing to keep fish that have much smaller home ranges and wouldn't know the difference between a 50g aquarium and the entire ocean, but sharks and rays need room to swim and hunt. they're solitary creatures.
and its not like you'll be building massive rock caves and underwater structures for them to hide amongst and maybe have a chance to feel at home - you're not building them a reef, your putting them in a tank.

sorry, i don't mean to attack you or imply anything about people who keep these animals. i'm sure there are many who keep them successfully. its just me being a lorax...

if you do keep rays or sharks, i'd just urge you to not see how many you can "comfortably" fit in the tank, keep like one or a pair and get a cool school of something. i think that would be a much happier healthier arrangement.