You almost have it, lucky. The idea of the slots is to handle varying water levels. We get alot of humidity, and therefore evaporation, in my area, so water levels could drop an inch in a few days. The water level ideally should always be near the top of those vents, but if it drops, there will be no interruption to flow, as I had in my last setup which used a series of 5mm holes for flow. Very sporadic, and hard to maintain with the varying levels.
The spary bar will be positioned down low in that rear compartment, shooting straight into the floor, not directly at each set of slots. It's my hope that shooting the spray bar straight down will give a gentle churning effect to the water surface, which will then trickle (not charge) thru the slots. As for velocity control, I think I'll mount an irrigation valve before the spray bar, or cut three of the six vanes from the impeller (effectively halving it's output), or do both.
If that's not confusing you enough, consider this for your design:
You could easily turn that rear area into a "sump" type filter. You could connect the powerhead outlet to the fittings at the bottom, drill multiple holes in the PVC "T" and cover everything (up to just below the vents) with media. This way, water would pump into the compartments at the bottom, and overflow out the vents, down thru the media at the back, up the PVC and out the powerhead again. That sort of system would have about 25L of filter volume (in my application) and likely handle a (relatively) massive bio-load. The reason that I discounted this plan, was that I wanted any waste on the floor of each compartment to have a better chance of being sucked away and into the filter system. This is my only concern with overflow systems used by Reefers (and some Freshies), waste doesn't float, therefore it sits on the substrate
hth!!
