Originally Posted by BillD
Sitting empty and dry will not harm the silicone. Fill them up and see if they leak.
Or ask the seller to fill them so you can see they hold water before you buy them?
That setup is just begging for a water bridge type arrangement!
Bio-Elite Aquarium Water-Bridge
With the tanks being so close then it shouldn't be too hard to do with a bit of flexible tubing!
(It also means you only need to run one canister filter for both tanks!)