I dont know which tetras you are talking about. But I have 10 neon tetras and they are in not the most ideal water conditions at the moment. Ammonia is 0 but nitrite is going back up due to a half tank gravel change so it's doing a mini cycle again. All tetras are fine and so are all the other fishes which are very delicate to water changes. I just keep changing 20% of the water every other day or so to relief them
make sure you leave the bag with the tetras in it for abought 40 minutes. I usually leave it for an hour maybea bit more, and add a bit of water from the aquarium to the bag every 10 mins or so. This will get the fishes used to the different ph and water temps. If you just put them in the aquarium from the bag they are going to suffer maybe die.