Ok let me add this. I just now did an ammonia test. It reads 0.50. That seems very little to be able to bring down a healthy fish in 3 weeks
This is deadly. Surprised they lasted 3 days, not to mind 3 weeks. Go get the buckets and start water changes. Then test again and make sure you've done enough water changes to not be able to detect any ammonia. There is no fin rot there, you are poisoning your fihs is my opinion. Sorry if I sound cross, but that's the truth. What are the nitrites?
Ok if this still doesn't solve the problem. If I do a water change and do all this stuff to prevent this, I still don't know what is going wrong. I came to this site for answers, not to just for people say how bad I am at keeping fish. I came to this site for one last effort to try to save these animals before I drain the thing and either sell it, or use it for target practice. Someone please tell me how to correct the tank and get it to be healthy and happy for years to come please. I'm begging you.
With all due respect, I have already answered this in post 5.
- Return the fish that you currently have.
- Drain, clean and refill your tank.
- Read the beginners section of this forum, paying close attention to the fish less cycling.
- Buy some household Ammonia and fully cycle your tank.
- Restock your tank from a new LFS avoiding tetras until your tank matures.
- Maintain good water change, cleaning and testing routine. (This means more than 1 water change per month)
- Enjoy your fish.