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I have a 4ft x 1ft x 1ft tank, with an Eheim 2224 external canister filter, and a internal fluval and two sponge filters running on it.
The tank is 25 degrees with soft water, ph of 7.6, kh 1 & gh 1, the tank has some oyster shells in it.
It has been running for nearly a year and was originally set up with a matured canister filter from another tank.
I changed a third of the water weekly with hma filtered water, and wipe the glass surfaces of the tank.
I use a thin layer of fine sand substrate (B&D Aquarium Sand) in the tank, with only minimal decor.
There is a light on the tank, on for four hours a day.
There is six rummy nose tetras in it, there was eight initially but i i lost two tetras over the past year.

I got nine Corydoras schultzei black from a fish shop in Glasgow a couple of weeks ago.
They are young and do not look mature adults yet, they are probably 1.5" to 2" in total length and look still to fill out a bit.

I changed a lot of the sand substrate last week because algae had been growing on the substrate, sucked the old sand out with my python, before adding the new pre washed sand.
i had previously had the light on for eight hours a day and halfing that time seems to have helped.
The sand got a good wash out before putting it in the tank, though it still did cloud a bit, but it settled quite quickly.

I was going to clean the tank today and saw this, around half of the corys have it:









Is it fungus, it's just with them all having it in the saame place, it makes me think it could possibly be heater burns??
What meds would you use for this?

It is hard to tell from your pictures. Fungus tends to be a 3-dimensional problem in that it looks like fluff as opposed to looking as if one painted a bit of white on the fish.

My initial though would be columnaris, but I hate diagnosing remotely, heck I hate doing it with my own fish let alone other folks. So what I am doing here is pointing you in a direction I think you should check out. Columnaris is one of the diseases with multiple strains. Some are highly virulent and kill fast while others are much milder and progress very slowly. This disease is sometimes called mouth fingus as in many cases it affects the mouth and the result looks like fungus but is not. Other typical signs are saddleback which is a white patch at the base of the dorsal or white patches on the body. In bad cases opens sores develop. Virulent strains can kill in 12-24 hours even before external symptoms are evident. It is a cintagious disease and under many conditions it can survive outside a host in the water. Dead fish are know to release becteria intio the water and need to be removed ASAP>.

If this is what your fish have, then an antibiotic treatment is required. It is not uncommon for fish with this disease to develop secondary issues which may include fungus.

As always this is just my thinking here and I could be completely wrong. However, it may offer a decent starting point. Good luck with the fish.

Hello Andrew,

The post by TwoTankAmin is spot on. You should take a look at the SeaChem web site as it lists some excellent antibiotic medications for your fish. Study the chart and read the descriptions. All can be added to the water and many can be mixed into food. I had excellent results using Kanaplex/Metroplex/Focus mixed in food with a little garlic guard to treat a little Corydoras Trilineatus for a disease similar to yours. These medications are "broad spectrum." "Broad Spectrum" means they kill many different types of microorganisms so you don't have figure out exactly what is infecting your fish. Being a Microbiologist, I can tell you it is difficult to accurately identify many fish bacterial/fungal/parasitic/viral diseases unless you have a fully equipped microbiology lab. That is why "broad spectrum" medicines are important.

http://www.seachem.com/medications.php

You say you have "minimal decor" in your tank. My catfish really appreciate these small ceramic logs even though they are made for betta's. Its pretty funny to see 2 or 3 snuggled up inside.

https://www.amazon.com/gp/product/B003Z ... UTF8&psc=1

Good luck. -Mike

Medicating whole tanks also wipes out the beneficial nitrogen-metabolizing bacteria, doesn't it? If so, then a hospital or quarantine tank is needed to isolate the fish, or if you treat the whole tank (which may be necessary), keep food to a minimum during this time to avoid excess water pollution, and do daily partial water changes. At least I think that's what you should do while treating as Mike and TTA mentioned above.

Also, FYI I got some black schultzei a few months back. They have repeatedly (3-4 times, almost monthly) become infected with something - perhaps velvet (oodinium) - which manifests as small slightly fuzzy lumps on the body sides. It's not ich, but clearly not fungal infections. I have repeatedly treated these corys with Proform C and it makes the spots go away. Other fish in the same tank don't get the disease, and so far none of my schultzei have died from it. I mention this because black schutzei are one of the very inbred strains of corys. So I'm speculating that their immune system may not be as strong as that of wild species of corys... Just food for thought.

Next time it occurs, I may hit the tank with Kanaplex or Bifuran+ as a follow-up treatment with the Proform C. I may also decide to throw away the substrate - perhaps it is harboring the pathogen even though other fish in the tank don't show any signs of disease (of course, the other fish may have "low-grade" or occult infections unbeknownst to me).

Good luck, Eric

Thanks for the replies.
I am in the UK and would need to order these meds overseas.
I posted a topic on Ian's site (Corydoras World) and he suggested trying some Primafix plus a little salt, i am going to go with that just now.
When i got back from work today i found two dead, but the others look alright (some still showing signs of fungus) and i have started using the Primafix, so I will see how it goes.

When it comes to the nitrifying bacteria, they are hardier than most realize. Their bio-film actually protects them from some of the harmful antibiotics and some of them are not the rught type to harm them. If a disease is waterborne than there is little alternative to treating an entire tank.

I have yet to wipe out my filters using antibiotics and in a planted tanks it is usually not an issue. But it never hurts to monitor ammonia levels jik.

As for doing water changes- If the day you need to do a cahange is one where medication is not added, then replace the amount of medication you removed with the water change. If you want to do a water change on the same day as you will be dosing, do the water change right before adding that day's dose.

AndrewC wrote: 13 Feb 2017, 23:15 Thanks for the replies.
I am in the UK and would need to order these meds overseas.
I posted a topic on Ian's site (Corydoras World) and he suggested trying some Primafix plus a little salt, i am going to go with that just now.
When i got back from work today i found two dead, but the others look alright (some still showing signs of fungus) and i have started using the Primafix, so I will see how it goes.

Just wondering how the Pimafix & Salt is working. Let us know. Thanks.