Help please! My rainbowfish is dying!

Tank
30 us gallons
One HOB filter plus a sponge filter
I cycled the tank for two months
I have a heater

Parameters
Ph 7
Ammonia 0
Nitrite 0
Nitrates lower than 5
Temp 78

Inhabitants
One rainbowfish
One dojo loach
Several plants

Feeding and cleaning
I feed some flake food. Most of the time I feed frozen because that is all the sick fish will eat. I change 30 percent of the water weekly.

Treatments
I am treating the infected fish with the required amount of fritz coppersafe.

Fish and Illness
I recently bought a rainbowfish with a small amount of fungus on his belly, even with treatment it has still been getting worse, fish will barely eat, erratic crazy movements all over the tank.
Just to clarify this tank is a quarantine tank

 

Sorry in advance for being so blunt.

fritz coppersafe.

If the fish has something you describe as "fungus", then why do you use this? Just on the off chance? You don't take a reflux med when you have a rash on your back either.

erratic crazy movements all over the tank.

Ok, the fish is beyond saving. Please put it down.

Also: Never buy obviously sick fish.

 

Fungus is often a secondary infection to a bacteral infection.
Copper Sulfate is a anti parasitic med & probably will have little to no effect against the bacteria.

 

Ok thanks. And just to clarify the fish was almost completely fine at the store, good colors, eating fine at first. I bought him with other rainbows and didn't notice the bacterial infection.

 

Ok, it made the impression you bought it knowingly.

Anyhow, if it already has problems swimming it's very unlikely you can bring it back.

 

Fungus is often a secondary infection to a bacteral infection.
Copper Sulfate is a anti parasitic med & probably will have little to no effect against the bacteria.

Sorry for the miscommunication the rainbow fish also showed signs of ich week after I got it but now the ich is gone but the bacterial infection has just started to develop. I was wondering what I should use to treat the bacterial infection now.

Ok, it made the impression you bought it knowingly.

Anyhow, if it already has problems swimming it's very unlikely you can bring it back.

Yeah sorry for putting the wrong idea out there
Okay I know I sound like a broken record but before there is any more miscommunication: I did NOT know if the fish was sick when I got it. I am NOT treating the fungus with copper, the copper was for the ich. And the fish is NOT swimming around like a chicken with its head cut off, it is just flashing and swimming erratically like once every 30 minutes. If there is any other miscommunications please tell me what I missed.

 

Unless caught early, bacterial infections are very difficult to cure & are usually fatal. The traditional antibiotics that are commonly recommended rarely cure & are now banned in numerous countries.
You might try a botanical antibiotic such as Microbe Lift Artemiss. Plenty of good on line reviews.

 

Ok thank you and sorry for being so vague at the start.

 

Okay I know I sound like a broken record but before there is any more miscommunication: I did NOT know if the fish was sick when I got it. I am NOT treating the fungus with copper, the copper was for the ich. And the fish is NOT swimming around like a chicken with its head cut off, it is just flashing and swimming erratically like once every 30 minutes. If there is any other miscommunications please tell me what I missed.

Those are literally VITAL informations that really made a completely wrong impression. Timelines and minute description of behaviours are extremely important.

Not many things to comment on:
- copper treatment against Ichthyophthirius is maybe a bit too big of a caliber. How is the loach doing with it? Loaches and catfish don't tolerate copper well. Catfish can be easily killed with it. Are you treating the other rainbowfish for ichthyo, too? It's highly contagious after all.
- "swimming eratically" is a term that usually denotes loss of position stability and/or buoyancy, and those are in 99% of cases the signs of critical condition onset and there is no coming back from that.

I can only ask for a picture now, or even better a video of the fish.

Ok thank you and sorry for being so vague at the start.

Happens. Just be careful and as precise as possible in the future.

 

Ok a closer look at the fish. It will turn its whole body around and flash its scales. It kind of swims with its body instead of its fins? Don't really know how to explain it better. The dojo loach is doing fine soon I am going to move it to my 55 gal community tank. On the fish's belly it has odd, white feathery growths? It looked like a bad bacterial infection. And sadly I'm thinking this rainbowfish is probably not going to make it. The other rainbows are doing great in their community tank but I don't think I can save this one. And I have been quarantining all of the rainbows for a month before they went in the tank and that one was the only one I had to keep quarantining.