Very long mouth rot

[confused_aquarist]

The water looks green there.

How often are you doing water changes and what percentage is changed?

Is there sufficient aeration to create plenty of surface water movement?

As the fish are from varying sources the issues are likely to be in your water, maybe contaminated supply or insufficient clean water or oxygen which can make fish ill, or make them more susceptible to pathogens.

Because most of the sick fish already display external symptoms upon arrival, and newly sick fish only become sick when housed together with another sick fish, I don't think water in my house is the issue. If water were the issue, it would have to be region-dependent. Often, fish are shipped from several hundreds of miles away. The water could be the issue.

This is day 2 after arrival. I started the tank yesterday, adding bacteria that cycles the tank within same day. I am planning to change water every 2 days to completely replace kanamycin and furan. The furan I am using turns the water green. I am adding an air stone bubbler no sponge filter in case this turns out to be TB because TB is difficult to eliminate once settled on rough surface, and also because I don't expect cycle to be established with antibiotics being present. It's possible that the bacteria I added initially was killed by antibiotic releasing endotoxins that stressed the fish. It may have been a smart decision to perform full water change before adding antibiotic.

It would also have been best to separate the pair for antibiotics treatment instead of cohouse. One would think that two strong antibiotics would stop disease transmission but maybe they didn't.

 

[confused_aquarist]

Still utterly puzzled by all those killies turning anorexic/floating/jaws melting.
The primary trigger is for sure stress-shipping, bullying, adding medicine, moving into hospital tank- things you would never ever expect a healthy fish to fall ill from. It got chased by alpha male -> stops eating floats and dies. I mean, wut.

Again I have kept this thread running for far longer than I wanted, which is good, but here is the real question-
Should I keep the eggs or throw them out? @GaryE @Fishfunn
I'm going to give away the parents for adoption if they ever recover so that way I don't have to risk transferring disease to my other tanks.

 

[Naughts]

adding bacteria that cycles the tank within same day.

Manufacturers may claim this but there are only 3 products that I believe in, and even then 1 day is pushing it. What product did you use?
Stress of an uncycled tank will make it nigh on impossible for fish to recover.