don't over feed for no reason, I don't see a problem with adding the fish, just keep water changes at a daily 10-20% daily for 2 weeks and you'll do fine. The fact that people fear adding to a bioload is irrational. The people that have problems are those that start up a tank and a week later assume they can max out their bioload, however if your tank is well established your bioload capacity is much higher than you assume, nitrifying bacteria are on basically every surface of the aquarium even on the glass.
My advice assuming your tank has been up for over a month and you still supplement bacteria with stuff like seachem stability is to quarantine the fish and then add them to your tank, for the first few weeks do daily 10%-20% water changes if possible and watch for stress. testing is way over rated and unless you calibrate your tests correctly they are useless, assuming you don't have professional water testing equipment that is.
as for the above recommendation to test every other day and wc only if your test tells you to. I find this is asking for a problem if you wait for your test to show signs of ammo it could already affect the fish better safe than sorry, just give the fish fresh water it is far healthier for them, rather than them swimming in waste water filtered or not