Luckily I don’t need have a ton to hide in it just a heater, return pump, and then all the filter media. Below is a picture of my initial design for the sump. It leaves 5.5 gallons worth of space remaining in the sump in the even the pump starts (I plan on putting a siphon break in it regardless). With the plan of a 40 gallon tank if I place the lowest part of the overflow 1 inch from the top I will never flood my sump. This also makes it so if my drain get plugged my last chamber won’t have enough to flood the tank. Any thoughts on the design would be great!