Catfish has skin lesions and the skin is peeling off. Very worried.

About 3 weeks ago I transferred my catfish who I’ve had in a 45 gallon tank for about 7 years to a new 75 gallon tank. About two days ago I noticed that he had some fairly large white spots on his back and close to his tail. As of today his skin is peeling off in three places and it seems to be getting worse. Last night before I did a 50% water change the ph was at 7.7, ammonia was.5 with zero nitrite and zero nitrate. I’ve been trying to treat him with pimafix but nothing seems to be working. I need some advice as I do not want to loose this fish. I’ve had him since he was about 3 inches long and he’s going on probably close to 9 or 10 inches now. In the pictures he does have a crippled tail from before I got him.

Here is a picture of all of him.

Was the new tank cycled before hand? Did you transfer the old media to the new filter? Zero nitrates usually means an uncycled tank.

For now I suggest keeping the ammonia down as much as possible. It wouldn't be a bad idea to move the fish to a smaller tank (say 20gals) to treat it with antibiotics. Clean water should help a great deal and antibiotics will hopefully allow the fish to heal up after a couple weeks.

Unfortunately, I wasn’t able to cycle the tank due to having to quickly change tanks due to a leak in the old one. I tried to transfer media but I think it dried out to much before I got it in. This afternoon I borrowed a used filter from a family friend and some of their tank water and added that to the tank. I’ve added some ammonia out tablets, and have gotten a heater for the water. If I had a small tank I would use it but at the moment all I have is the 75 gallon. But I pulled all the plants and the log he hides in so I can keep better track of him. The only other fish in the tank are Feeder minnows so they are expendable. I also added some tank start bacteria that tetra sells to try and jump start it two days ago before the 50% water change.

Poor water quality doesn't cause this but if you had a power filter on the smaller tank you should have simply moved that onto the big tank.

Monitor ammonia and nitrite and if there is any reading then do a 75% water change using water that is free of chlorine/ chloramine.

Pimafix & Melafix won't do anything for this.

The fish has either injured itself on something sharp or has a flesh eating bacteria.
What ornaments are in the tank, is there anything sharp that could cut or scratch the fish?

Remove any sharp objects that might scratch or cut the fish.
Is the gravel from the old tank or is it new gravel and how sharp is it?

Do a 75% water change and complete gravel clean each day for a week. Make sure any new water is free of chlorine/ chloramine before it is added to the tank. If the problem gets worse then you will need some medicated food and you could feed medicated food anyway to try and kill any bacteria in or on the fish and help it heal.

Medicated food might be regulated in your country and you might require a veterinarian to prescribe you with the drugs. A fish vet should be able to take swabs of the area and culture them, as well as provide you with the medication, however it will cost a bit of money.

I have a hospital tank set up but he’s so weak I’m afraid the stress of moving him will end up pushing him over the edge. I just went ahead and added amoxicillin to the main tank in a hope to get him up and moving. The only thing in the tank with him is a few rocks that have always been in the tank with him the gravel is from the old tank also. It was slightly cleaned and added back. And the skin is only falling off on one side but it is still getting worse. It turns white then slides off. Also I’ve noticed that the muscles have started to turn white also

These are pictures taken just before posting

I'm pretty sure that is a flesh eating bacteria. Amoxcyllin will kill the filter bacteria but will hopefully kill the bacteria in and on the fish too.

If you set the small tank up using water from his main tank, you could scoop him up in a bucket of water and transfer him into the smaller hospital tank. You can also remove the gravel and rocks/ ornaments from his current tank so the anti-biotics work better.

You normally treat every day when using anti-biotics, and you should wipe the glass down, clean the substrate and do a 90% water change before retreating. The cleaner the tank the more effective the anti-biotics.
Wash the filter out each day too.

Make sure there is no carbon in the filter because it will remove the medication from the water.

Don't feed him for the next week. Check water quality daily and if any ammonia or nitrite, do a 90% water change and retreat with medication. However, I don't know if it will work. That's pretty bad.

To work out the volume of water in his tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.

The small tank is conditioned tap water which was given a double shot of cycling bacteria and some water conditioner and run for about an hour before the anti biotics where put in. It’s just an empty tank with no gravel. If I can scoop him up I’ll transfer the air stone and the heater over and shut the main filter down as it’s to strong of a current for such a small tank.

I would use the tank water he is in to set up the small tank. That way there won't be any change in water chemistry.

There is no point adding cycling (filter) bacteria to the small tank if you add anti-biotics. The medication will kill the filter bacteria within minutes of being added to the tank.

Do you have any other fish in the big tank? If not then if you move him into the smaller tank, flush the main tank out several times and let it all dry out for a few days. Then start again.

I tried you idea about the tank water to help with the transfer and it seemed to work. But He keeps rolling over on his back and side in the areas where there is some undisolved amoxicillin on the bottom. He does seem to be slightly more active. Though now that he’s in the new tank and his breathing has kinda went back to normal.

The big tank has some small feeder Minnows in it at the moment but I also nuked that tank with the amoxicillin. I don’t mind if I loose a few minnows but I do mind if I loose my catfish. He’s the only fish I’ve every really liked and I’ve had him so a long time.

just monitor him and see how he goes. If the anti-biotics are going to work the holes/ wounds should stop getting bigger within a few hours. If they continue to get bigger after 24 hours the medication is not working.

If the medication does work, you will need to keep the anti-biotics in the water for at least 1 week (preferably 2 weeks) to make sure the bacteria are dead. You want to keep treating for at least 1 week after the wounds have stopped getting worse and started to heal.

I may have added one to many antibiotic capsules while I was freaking out, would that have any adverse side effects?

a slight overdose should not harm the fish but a massive overdose could kill it. If it is overdosed the fish will usually breath more heavily and dash about or try to get out of the tank.