Four of your brackets are taking all of the load. The outer brackets are only holding the rods in place. What you've created is a simple lever on the inner brackets and you're actually multiplying the forces there. You've got straight line force on wood fibers. Start sloshing water around added to your actually moving the tank and you're just asking for trouble. We're only trying to help you avoid a problem. Trust me, I've built a few things that sounded good, worked in theory, and actually worked great in practice. For a while. Fortunately those instances have been rare. Sort of. Last one was a lumber cart. Looked great though
Recedite, plebes! Gero rem imperialem.
Quote me as saying I was misquoted.
Once you get rid of integrity the rest is a piece of cake.
Here's to our wives and sweethearts - may they never meet.
If you agreed with me we'd both be right.