Mass Deaths in Tank

[bettas_in_DE]

Hello!

This is my first post here!
I had a tank that was a sorority for bettas. I added in a new fish that clearly had something wrong with it as I was dumb and didn't QT her! All of the bettas in the tank DIED! But they were not the only fish in the tank. I have endlers and guppies and a pleco in with them as well and none of them have died! My water parameters are fine. Ammonia 0 Nitrite 0 Nitrate 5. It's well planted.

I have been treating the tank with API General Cure. Remaining fish are doing well. I am assuming that the stress from sorority life made what i believe to be an internal parasite just act faster. I noticed that some girls were not eating and some had stringy poop. No other signs of disease though! The other fish are all eating and have normal poop.

Will treating the tank with API General Cure be enough to treat the tank? I want to add new fish in eventually, but not for a while! The treatment will be finished by Saturday and I will cap it off with a large water change!

Thoughts?
I will be bleaching equipment, but if the other fish are all doing well, I don't think I would need to bleach the whole tank right? I would have no where for my other fish to go!

 

[bettas_in_DE]

Well I am guessing what I am doing it working as I was stupid and seemed to have cross contaminated my male bettas tank and he was looking rough! But after using the API General Cure he is back up and swimming and flaring at his reflection in the side of the tank just like normal! I am going to assume that the stress of the sorority just made everything worse for the girls which is why they all (well 8 of 9) died and none of the other fish in that tank died. I was afraid it was something like Columnaris, as I always jump to worse case scenarios, but none of the fish had the signs of that nor any cotton mouths! I don't think I will be getting any new fish for quite some time after this experience though!

 

[NickAu]

Im sorry but 8 Betta females do not just die of stress all of a sudden.

I have a sorority.

 

[bettas_in_DE]

I’m aware. I’m saying that there was an infection or parasite that one of them had and the stress from them being in the sorority must have weakened their immune systems this allowing the parasite to do what it does and kill the fish,

None of the other fish are dead from that tank, just the girls. I have one that is actually still alive and she is acting normal and eating and pooping. I know that for a fact one of them was refusing to eat and then she shortly died.

And a betta from a different tank had very similar symptoms who I treated with API General Cure and he is back to normal. If I wasn’t so paranoid that the girls were dying from fighting, as two actually were badly beaten, I would’ve treated their tank too and I probably could’ve saved more! It’s a lesson learned and I will never do a sorority again!