I just posted this on another thread...but it's the exact same thing I'd put here...so forgive my copying and pasting
That's great news!
If it's going to be a significant amount of time before getting fish, there's nothing wrong with keeping it at 4ppm. The only downside is that the no3
will jump back up and you'll have to do more water changes to get them down before stocking.
If it's only gonna be a couple days, you can keep it fed with just around 1ppm every day. It takes several days before the bacteria begins adjusting to the lower level of ammonia...so as long as you don't let it go too long at the low dose it'll be fine.
One thing I'd do is turn down your heater now so you don't forget. You don't want to get new fish just to cook them when they get there
Keep us posted and remember that we require pictures