Yep, you need to keep feeding the tank or the bacteria start to die off. You can skip a day, but a week is too long. At the end of a week, you might have to start from scratch.
A raw shrimp or 2 is one way of providing the ammonia source, although it can be smelly! you can also throw in a pinch of fish food a day. <Get an auto feeder.> One bonus is that the cycle will continue when you are gone, and might even be complete when you are back.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.