Help! What is this?

[Goshfush]

Hello, 

i purchased a batch of 5 Corydoras a few weeks ago. One of them had frayed fins when I got them but I assumed it was because they were in with some barbs at the aquarium stores. The fins haven’t got worse or better but I thought they just need time to grow back. Now I’ve noticed that behind one of the fins is this like bright red “bubble” ulcer thing behind the dorsal fin. There is also some redness under one of the pectoral fins and another lil ulcer thing on the pectoral fin. The fish is also no longer active and I’m not sure if it is eating. The other Cory’s all look perfect. I put it into a small quarantine tank and put some kanaplex in but I don’t know whether it’s the right thing. I tried to give it some repashy today but so far it’s just sitting in the same spot ignoring the food. I thought maybe it is Septicemia but all the photos I have seen online I haven’t seen the bubble like ulcer thing. Can you help? Thanks so much for any ideas in advance. 

tank parameters (before the move to quarantine)

Amm: 0

ni: 0

na: 5

GH:7

temp: 26

 

 

[Colu]

Possible injury that caused the  ulceration looks like a secondary bacterial infection I would do one full course of kanaplex and I would add a small amount of aquarium salt 1 table spoon for 5 gallons that will help reduce any possible fluid buildup in the lump aid Gill function and add essential electrolytes @Goshfush

Edited February 27, 2023 by Colu

[Goshfush]

Hi @Colu Thanks so much! Hopefully that is all it is and can heal. I have some aquarium salt and home so I add it in now and the kanaplex is in already.  I’ll keep you posted and thanks so much for your response! I really appreciate that you take the time. 

 

 

 

[Goshfush]

Hi @Colu

I thought I would give an update and see what you think! So I treated with Kanaplex and a malachite green fungal treatment and aquarium salt for a couple of days. There wasn’t much improvement I did a water change and re-dosed I also added metroplex. 
The lump behind the dorsal fin has now shrunk a lot (yay!) but the fish has now developed a few smaller ones. I’m at a bit of a loss! Could it be a parasite? I can’t seem to find anything online that looks like it!! The photos look a bit green but the spots are actually a blood red.  Thanks so much for taking the time!!!

[Colu]

Doesn't look like a parasitic infection possible bacterial infections  what I would is treat with medication with a different active ingredient I would do a course of maracyn2 in food active ingredient minocycline is a broad spectrum antibiotic treatment and also has anti-inflammatory properties feeding a small amount twice a day for 7 days  and I would keep the level of salt at 1 table spoon for 5 gallons@Goshfush