This Younger Spouse
Fish Fanatic
I'm no expert, but my reading indicates that ammonia and nitrite poising can be sneaky. It weakens the fish, and weakens their immune systems. It shortens their life. What you really don't know is how well cared for this tank and these fish were before you got them. If you bought the whole thing as a package and there was no test kit with it, that to me would quite possibly indicate that ammonia and nitrites were slowly taking the life away from your fish.
Then all the radical fluctuations in ammonia and nitrite could have been the straw that broke the camel's back. If I'm wrong about any of that, someone certainly will politely correct me.
I did a lot of tropical and saltwater fishkeeping 25-30 years ago, very successfully, and when I got back into it just a couple months ago I was shocked almost immobile by all the differences in how things are done now. Things have come a VERY long way. I had a lot to learn in a short period, basically totally relearning the hobby.
What I think your best option is at this point is to rehome every living fish you have, either at a LFS for credit, the goldfish going to the zoo, or with a responsible and knowledgeable fishkeeping friend. It may or may not be feasible depending on how many fish you have left.
Then completely clean out the tank (but hold on to your filter media), and do a fishless nitrogen cycle. The filter media you have already has some bacteria colonizing it, based on your readings, so that might help speed up your fishless cycle.
There is a complete primer on fishless cycling here.
Trust me, I know how frustrating it can be making these mistakes, and you are learning quickly. Sort of a trial by fire. We are all wishing you the very best of luck, Kling!
Then all the radical fluctuations in ammonia and nitrite could have been the straw that broke the camel's back. If I'm wrong about any of that, someone certainly will politely correct me.
I did a lot of tropical and saltwater fishkeeping 25-30 years ago, very successfully, and when I got back into it just a couple months ago I was shocked almost immobile by all the differences in how things are done now. Things have come a VERY long way. I had a lot to learn in a short period, basically totally relearning the hobby.
What I think your best option is at this point is to rehome every living fish you have, either at a LFS for credit, the goldfish going to the zoo, or with a responsible and knowledgeable fishkeeping friend. It may or may not be feasible depending on how many fish you have left.
Then completely clean out the tank (but hold on to your filter media), and do a fishless nitrogen cycle. The filter media you have already has some bacteria colonizing it, based on your readings, so that might help speed up your fishless cycle.
There is a complete primer on fishless cycling here.
Trust me, I know how frustrating it can be making these mistakes, and you are learning quickly. Sort of a trial by fire. We are all wishing you the very best of luck, Kling!