@Rocky998 ....please do not get so frustrated
The issue here is that you stated in another thread that you would wait a month or two before replacing the fish. You then got all in a panic over some legislation that might never get into the statute books and went ahead with replacing the fish without really thinking about how the existing fish would react.
@itiwhetu and many others, myself included, have watched you gradually build up your aquarium well only for one stupid mistake and a rushed mistake turn everything upside down. He is furious with you and I guess many of us are cos you asked for advice but never took it, so of course he will display his frustration at you for that.......he is absolutely right that the fish depend on you 100%, they cannot tell you if there is anything wrong or if they are uncomfortable or scared, you have to learn every aspect of these animals...not just how to care for them, not just how to maintain their habitat but to learn about their emotional and physical needs and that includes not moving new fish into the same territory right after another has died.
Think of it as where you live and someone replaced a relative of yours and you had no say or opportunity to get ready for it...you would not be happy, you would not be welcoming
A dog will bite you when it is angry at you
A fish that has established its territory and then a new fish of the same species just bounces on in there and starts taking over territory is going to be met with a certain amount of dislike and often violence
At the end of the day you are responsible for researching the fish, their behaviour, their warning signs, their body language...not just the basic weekly maintenance routines.
This has been a very important lesson in how not to run an aquarium and how not to panic buy......cos yes, it cost you financially but you will get that money back in a few months....the fish doesn't have that luxury, your haste in replacing it cost it it's life.
You are going to have to suck it up when people get frustrated with you, not just in this but in life generally. Mess things up and people will not hesitate to tell you and if, like this it is mostly your own fault, accept it, learn from it and don't repeat it.