RE: Question about planted aquarium and fishless cycling
I am gladly to be able to help.
Usually I would continue to add ammonia for extra a day or two to make sure the aquarium can covert all of the ammonia to nitrate and to give the bacteria colony time to stabilize itself. A large percentage water change is needed to remove the excessive nitrate and to restore the water buffer. I'd do a 70% water change, or even do it twice in a row. Just to make sure the filter media stay wet the whole time.
By the way, have you already added the fish? Zebra Danios are known nippers. Guppies' long fin will make perfect target for them to nip on. Guppies are also slow moving fish, while Zebra Danios will zip around the tank. I wouldn't recommend to have them in the same aquarium as any slow moving, long fin fish species. Even if the Zebra Danios somehow leave the Guppy alone, they will definitely grab the food before guppy can even get there.
I would also test the water at least once a day to make sure everything is alright. Feed fish lightly will also minimize the amount of ammonia produced in the system. Once a day is enough with as much as they can finish all under a minute.
Good luck with your new aquarium! Please sure some photos when you are all set.