I think I poisoned my new fish!

[TaylorRhea]

I started a round of quarantine with a new set of neon tetras and a hillstream loach on Thursday 5/20. Everything seemed fine and now within the last twenty four hours they have all died. I finished a round of quarantine with different fish a week prior. Had cleaned the tank, filter, and heater with a 1:10 water to bleach ratio. Everything was rinsed multiple times, and fully dried between quarantines. Did I do something noticeably wrong??? Or is there a better way to sanitize? Any help would be great I’m so devastated. 

[Fish Folk]

34 minutes ago, TaylorRhea said:

I started a round of quarantine with a new set of neon tetras and a hillstream loach on Thursday 5/20. Everything seemed fine and now within the last twenty four hours they have all died. I finished a round of quarantine with different fish a week prior. Had cleaned the tank, filter, and heater with a 1:10 water to bleach ratio. Everything was rinsed multiple times, and fully dried between quarantines. Did I do something noticeably wrong??? Or is there a better way to sanitize? Any help would be great I’m so devastated. 

It is possible that you may have killed off your colony of beneficial bacteria. Ammonia spikes easily without bacterial filtration to convert through the nitrogen cycle.

[Hobbit]

I assume you used dechlorinator when you set everything back up? That should have taken care of any residual bleach. 

If you did use dechlorinator, I’m guessing @Fish Folk has it right, and you got a bigger ammonia spike than you may have been expecting. One way to protect against this is to keep a filter sponge in your main tank and move it to your quarantine tank whenever you set it up new.

That, or the fish may have been sick when you got them. Sometimes that happens, too.

Sorry you lost all your fish! 😞 Don’t beat yourself up though. These things happen to everyone at least once in a while.