If it was properly cleaned you won't have a problem. But cleaning it properly by hand may be difficult, using boiling hot water or steam, even if you use disinfectant there is a minute chance that all the pothogens will not be killed. If you look at the way that medical utensil's are cleaned most of the time it is done with steam. That being said Imo and Ime I believe that if you do a reasonable job on cleaning the cup with very hot water and disinfectant you will be fine, that is if you can handle the fact that you have had it in your tank before cleaning.