My not so over adventures over the last week. (long)

It starts like this...

I start getting that itch for new fish about 2 weeks ago and figure its to add a couple bigger fish to my 55gallon.
After a thread here I decide on Gouramis... Do a bit of quick research and figure I know what I am talking about.
So I drive ~30min to a store that I like since their stock always looks very healthy. I get there and choose 2 blue Gouramis and 2 gold ones
(those had been recommended by someone as well and I liked how they looked over the pearl ones and I mistakenly believed they were all color morphs)
and then I also grab some Lemon Tetras to fill out the school a bit.
I bring them home and acclimate them over 45min or so and then add them to the tank.
All seems well.

The next morning I find one dead tetra.. I am not entirely surprise and write that off.
Everyone is fed..

The morning after that I find a small dead Cory and another dead tetra.
The tetra i write off as another casualty of the move and the Cory i just tell myself I am being over cautious and that since I have so many in the tank i just didn't see the occasional die off every now and then.
I feed the tank and go to sleep...

The next morning I am a bit overwhelmed with what to think.
2 dead Corys and 2 dead tetras.
Now I begin to panic.. after a bit more research and really conflicting information I am left to believe it is the Gouramis.
I watch them like a hawk but fail to see anything that would indicate that it was the Gouramis causing these deaths.

It is now Sunday and I awake to nothing.
Sunday was a good day...

Monday morning.. 5 dead Corys and 2 dead tetras.
That it.. I call up the pet store I bought them at and ask if they would be able to take the fish back. They said sure and would give me store credit.
I mention I did not have my receipt, person on the phone says no problem.(the guarantee was 48hours and ended up throwing away after that.)
I go to work upset..
I come home and find a couple more dead Corys..
I bag up the Gouramis and drive 30min to the store.
I explain my situation and they then tell me they can take them back. But a sale had started and they would only be able to give me half price... With a blank stare I say fine.
I don't want to introduce anything knew to the tank so I grab some frozen food with the credit and come home.
Thinking this is over I try to forget about the entire misadventure and chalk it down to a somewhat expensive learning experience.

Its now Tuesday morning and I wake up to 4 more dead Corys. Up until this point it has been the smaller ones. I bread them recently and most from that batch are only just over an inch. However, this morning one of the adults is dead..

I tested all the water parameters.

• 78 f
• 7.8 ph
• 10 gh
• 0 ammonia
• 0 nitrite
• 10-20 nitrate

My only hope at this point is that those were ones that were abused by the Gouramis and had just yet to die last night. However, they show zero signs of injury or disease.

This whole event has been a rather humbling experience... knocked me back down to newb status.

Thanks for reading.
Any relating to my frustration or suggestions on what to do from here would be appreciated as my family thinks I am crazy for being this annoyed about the situation.

My plan is to hope that I don't wake up to more dead fish tomorrow and if I don't I am going to leave the tank alone for a couple weeks before I do anything else with it.

5 more dead when i got home from work from earlier.. They have zero signs of any problems... I do not get it...

That is reassuring. I suppose it could still be stress.. I am curious how the next couple days will be. Anyone have ANY ideas.. just an explanation would be at least some form of relief for me. I guess everyone has to learn to quarantine the hard way...

I finally saw one of them die, basically it was looking normal and then all of a sudden it spazed out swimming erratically toward the surface and then died(as far as I could tell/no gill movement) about 30seconds later. A MAJOR THING I NOTICED is that their eyes seem to get bloodshot.. don't know why I did not notice this before but it seems to be how they are.

I have had a bit of a realization as to what it could be. The same day I bought the gouramis I did a 50% water change using a new rubber coupler to replace an old one on my python... I let water run through it for about 10min before using. This was the same thing I did the last time I replaced it(about 1yr ago).

Perhaps some type of chemical poisoning? Sigh this is a really rough learning experience...

I am doing a 70% water change right now with buckets and adding activated carbon..

Alright when I have completely taken down the tank and rinsed/wiped down everything I saved the biowheels but rinsed them very well in dechlorinated water. Right now the fish are in a 10gallon however they are still dieing fairly rapidly..

4 days later and they are still dieing.. however it seems to be slowing down. I have been changing water every day in the 10 gallon so I cant imagine its anything left in the water.

I guess it could still be from internal damage that was caused from whatever the initial problem was.

They are still dieing in the same fashion... very randomly on any of the completely healthy looking and acting corys they will all of a sudden lose the ability to swim normally and they will propel themselves in random directions for about an hour.. then they will die. when this first started happening they seemed to have red eyes when they were dieing/dead. Now I have not observed that.

This has happened about 30 times now in exactly the same way.