As others have stated, It all depends on what caused it. It could be as easy as draining and refilling. This will preserve bacteria as long as surface areas stay moist.
Do you have a sand bed? How deep and how often do you clean it?
Also saw this was a 10 gallon air with bioballs and skimmer running refugium light and looks like a fairly tight lid for display.
How often was light and skimmer on for a day?
This was also setup in January based on posts so how often, when and what was the amount of last water change?
Do you have an air pump.
What I am possibly thinking is an oxygen issue and not enough gas exchange unless skimmer was constantly running 24/7 or the lid didn't cover entire display and good surface agitation.
I keep a glass lid that seals the main display. So my back chamber has an air pump to add more contact to oxygen.