Layout looks pretty good!!!!! Not sure I agree with the Chemi pure in the last chamber before the return pump. Depending on the water height of it dropping could produce micro bubbles....If anything I would force the water to run under that last baffle before the return pump. That way it would allow any bubbles to be forced to the bottom and have to rise to the surface to pop....
Just remember not to drill the return from the pump to low in the tank. I caution this because when power goes out as your probably aware the water will drain to that level. I would drill the return tubing with a siphon break hole to prevent that....HTH