I had that happen in my old tank setup. Too much light caused the overflow tube to grow with algae causing the water level to rise causing a minor overflow that eventually turned into a puddle on the ground.Of course! The overflow is providing "refuge" to the pods by limiting predation, so whether or not you intend it as such, it will serve the same purpose as a traditional refugium when it comes to maintaining a pod population. Now, if your overflow box gets a decent amount of light, and you are committed to regular maintenance, you can also let algae grow there for nutrient export. Just make sure the algae doesn't interfere with the drains, etc.