You are going to keep your sensor for the ATO in the center chamber in the back. This will keep the water level throughout the whole tank. Make sure that the sensor is positioned where it will turn the ATO off before it reaches the top of the baffle on either side. You want to keep the water level lower than the last baffle so the water is forced to go through all chambers in the back.
+1000. Just wait until #2 comes along and instead of adding modules to your Apex, you're paying for trips to the doc-in-a-box for some sterile super glue thanks to #2 inventing a weapon out of what you thought were harmless stuffed animals and assaulting #1.
That Avast probe holder does look nice back there. Excited to get mine in.
Stupid ATO newbie question... in relation to the compartment dividers in the sump area, how high do you guys keep your water level? I haven't replaced the original media baskets yet, so it seems like a slightly lower water level forces more water to flow straight down out of the overflow and through the media. Raising the water level up closer to the top of the compartment dividers seems definitely makes things much, much quieter but it looks like more of the water is flowing over top of the media when it comes through the overflow. My assumption is that I'll want to keep the water level up closer to the top of the dividers to reduce the noise, etc... and that the incoming water will be forced to flow through the media rather than around it when I replace those media baskets with the InTank baskets. Am I on the right path there?