Question about JBJ nanocube

That little hole in the first overflow chamber is a fail-safe. It evens out the water level between the main display and all 3 chambers when the power goes out.

[Snaz]

I have an aquapod with similar chambers. If the return pump returns water faster than the overflow the pump chamber will run dry. Check and clean all paths that the water flows back to the return pump so it does not run dry.

[Oilers]

I took out everything in the back chamber and cleaned it last night. Everything seems to be A-okay now. Thanks for the help everyone.