Hey bud, welcome to the fold.
Where you from in Oz?
If your ok with some discussion, do you mind we talk your designs.
If ive got this correct, 3 in-series canisters with isolator taps feed two spray bars & a focal return. Greens your dump pipe plenum.
I dont know if you have the latest & greatest external filters these days that are design to be bullet proof, however in my own observations, they generally tend to not handle a force fed line to well, nor appreciate a lesser or greater resistance in series due to multiple pumps.
Once it hits the T, its down to the path of least resistance. If the forcing pressure is less than the head loss value, then you could see some wet action.
To calculate total volume, multiply all three dimensions by each-other then divide by 1000. LxWxD/1000
Working volumes just the same, just at water level.
Your tanks are lined up well, always level on your working heights.
Fish bridge is a nice touch though.
Thoughts below...
a) Keep the bridge uniform, so lengths equal on both side - The pressure is greater on the left tank & at a greater depth, so it can cause an issue.
B) all syphoning points need to be accounted, without a decent check system your dump pipe becomes the lowest drain point. Or if you have the canisters stop the flow, then thats worse, as your drain system is not free flowing which opens the door to yet another issue.
c) even with the fish bridge, i would factor a bulkhead bridge for redundancy.
d) You have a sweet design, id take it to the next level & throw any container under that puppy, even if its a rubber maid & return pump. Then you could open its potential.
E) great sketch up, it sells your idea. Now I want to introduce you to google sketch up.
