Calgary zoo rays die due to human error

[jslaney]

Not to question the big wigs, but that is a relatively shallow tank with a huge amount of surface area. Even if there was no water movement does low O2 make sense?

Unless bacteria started using all the O2 (which would be noticed by green water) this does not seem possible.

You could probably shut off all the pumps and still have enough O2.

What do you guys think?