Empty tank as a sump - No compartments

[Animal-Chin]

Its all about the skimmer and the water level. I had one witout baffles and now one with and I would never set up a sump without a skimmer compartment again. You auto top off works way better too if its in a small compartement. Plexy glass and fishtank safe silicone is all you need. make sure you get fishtank safe though, some silicone will leach into the water. Your LFS should have some...