Hi, if you have an established tank and can use some of the filter media or gravel, something that has been in the established tank, add it to the new tank and add the fish within 24 hours so that the good bacteria does not die off. Do not rinse off gunk in tap water, remember to use de-chlor water. Be sure to monitor readings and do weekly water changes at minimum. The good bacteria is on the hard surfaces no suspended in the water.
If you are going to add ammonia, do not add fish until you have gone the full cycle which can take up to 6-8 weeks.
Lots of live plants also neutralize the harmful bacteria cycle.