New Silver Tipped Tetras introduced to new tank and now dying

[ZachnJess]

My husband and I just bought 5 young silver tipped tetras on Thursday. We have a new planted tank only about a week old and we wanted to cycle with fish. We introduced them relatively slowly, we let them float for about 1hr and tried to slowly add our water into their bag before releasing them in the tank. They were super skittish the first evening and split off individually and hid a lot of the time. We did feed them a little and they ate. The second day they seemed much more comfortable and were very active and already coloring up. They showed interest in the little food we gave them, but we tried not to feed them too much. We did notice some aggression among them starting, some chasing, and one in particular was getting harrassed almost constantly by all the others. This morning they are completely different. They are sluggish and having trouble staying level. Two were dead in the morning and another died later, the other two are moving very slowly and were having trouble staying level. I noticed that they are near the top like they were gasping for air and there are some bubbles on the surface of the water. Our temp is at 78F, PH between 7.4-7.6, GH is low (we have soft water from the same area as the aquarium we bought them from), ammonia was 0ppm, Nitrate 0ppm, Nitrite 0ppm. I really don't want to lose more fish and when we do introduce more to the tank I don't want them to die right away either. Any ideas what we're missing?

[Colu]

It could be low levels of desolved oxygen I would do a 25% water change and add an extra air stone

Edited May 8, 2021 by Colu