Re: the two in the back...that was a rhetorical question.
Kinda me goin "huh?"
Could you do some measurements of the baffles to find out how tall they are (just the ones that go to the bottom)?
I'm thinking the front compartment where the tall baffle is was planned to be a refugium. Then I think the water is supposed to come in through that chamber next to it, go through some filter media into the centre chamber. I think the centre one is for the skimmer, and then the water goes out through the left. I would add another baffle on the left before the water goes out.