Hi, I am relatively new to keeping aquariums but I have done a lot of reading and have gotten a lot of advice. I have a tank that is cycled as confirmed by a water test that said the only problem was the ph was a little high but not dangerous. It has been running for about 3-4 weeks now. The first day I added quick start and beneficial bacteria which I know isnt the same as cycling but I thought it would at least help. I let it run for a little while then added a goldfish to help cycle as well. About a week later I got the water tested and was told that it was all good. A few days later I got my peacock gudgeon from a very well reviewed local fish store. I had him for about a week and a half and now he is dead. This morning he was swimming fine and nothing seemed to be wrong. This has made me re think everything since I dont know what is wrong. Did I do something wrong or was there something wrong with the fish?