Water Smells Bad

I opened the top of my l30 ultra and it smelled pretty bad. I cleaned the used water tank. Is there anything else I can do to prevent this? There was barely anything in the used water tank, and I empty it when it's done mopping. It had water in it for possibly 1 day.

You should rinse the dirty water tank after emptying and with a paper towel, dry it
All the bacteria in the dirty water droplets, will still smell   

I add just a few drops of essential oil to my dirty tank when I clean ( lavender, lemon, just what I may have on hand)  

Hello,

Please confirm whether it is the base station or the robot that emits the odor. If it is the base station, you can clean the sewage tank and the bottom of the base station, and check whether the dust bag is full. You can replace it. The water tank and the bottom need to be cleaned regularly. If the robot has an odor, you can clean the dust box and rag.

I hope the above information can help you