No criticism from me, I'm just relating what I found out using a proportionally smaller, thicker and therefore stronger canister, and it had a built in silicone O-ring. It worked great on a stool 7" below the tank water line for as long as I ran it for months, but not under the tank not even 1/2 way under.
Doing it again I would use rigid, non pliable, water proof, re-enforced container with O-ring compression seal. Actially Im making one now but I wont post until its been tested, another 2 weeks.