This was a sump I built for a LFS near me. The challenge was making a sump big enough to hold water from about 20 tanks draining into it, and be able to handle a new shipment of livestock that arrives. All those bagged items quickly increase the total system volume. And then throughout the day, water is taken as each piece of livestock is sold, dropping the total system volume.
I ended up making it too big. After watching it for a period of weeks, I noticed the water rose and fell about 2" depending on what was transpiring.
You'll notice all the eggcrate. Acrylic partitians held the eggcrate in place. This central compartment is the refugium zone, and the eggcrate was extra tall to assure that the macro algae wouldn't be able to migrate into a different section of the sump.
Dual drains filled the first area, and floss trapped organics and waste.
A Mag 24 was used as the return pump.
Another principle behind the eggcrate instead of a solid baffle was to share the refugium and return zone water level. This prevented the final zone from dropping rapidly throughout the day. Instead, any removed water would gradually drop the level across two zones, which worked out nicely.
A large skimmer filled the first zone. This sump was built in 2007 and ten years later they are still being used at this store.