HELP All my fish are dead or dying

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Aquarium Advice Newbie
Jun 3, 2024
Pennsylvania USA
Thursday evening I noticed my tank was a little cloudy. I had 2 Chinese algae eaters, 2 white skirt Tetras, giant Danio and a Rainbow shark. let it go overnight after changing filters, I was a week behind. Friday i noticed my Chinese algae eaters were pale and looked like they were shedding. I did a multi test strip, showed high alkalinity. I took the strip to my fish store to get advice, have never had this problem before. They suggested a 20% water change. I did that Friday evening. Saturday morning they were both dead. I went back to my fish store, told them what happened and wanted to make sure I had the proper chemicals. I did the usual, fill a container with their water, gently transferred fish to the container, everyone was doing fine. Got the tank cleaned, tested before chemicals, after chemicals, acclimated the fish to the new water, everyone was fine. I individually transferred the fish, starting with the larger Tetra, then the smaller, the Rainbow and the Danio swam into the net, Rainbow first. Once all were in the tank I saw the RS swimming upside down and vertically, this is new for him. I started looking up what it could be. By the time I was done looking it up, my smaller Tetra was in bad shape, within 30 minutes it was dead. Tested water again, all in proper condition, then the RS was doing the same, within the hour he was dead. This morning(Monday), the larger Tetra is not doing well, I'm sure it will not last much longer. The Danio is not swimming around normally. What did I do or what happened in the tank that is most likely going to kill all of my fish? I'm crushed that I did something wrong! Sorry for the length😢
Please take a read through the "unhealthy fish" sticktly and give as much information as you are able. Saying things like "proper conditions" means nothing as we have no idea what you might consider proper.

Also what chemicals are you adding? The only chemical you need is water conditioner. What water conditioner are you using?
This is what I use, the test strips weekly, AquaSafe for cleaning and 20-25% water exchange, the EasyBalance only when nitrates are high but use 1/2 - 1/4 dose. They aren't fed all the food shown everyday, except for the TetraMin. They get TetraMin in the morning and evening, afternoons are one of the others, ie., small pinch of Blood Worms, next day, Tubifex worms, then another the Veggie, a couple of times a week they get Tubifex worms because they loved them. All food is well within the expiration dates, also.


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Like i said, go through the sticky and answer all the questions as thouroughly as possible.

Those test strips dont test for ammonia which is the most likely parameter to be off. And strips arent accurate, you cant trust the results they give you.

Take a read through the following thread for first aid measures until we can figure out whats going on. Take a sample of water before doing water changes do we know the conditions in the tank.

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