Julie cory turning white?

[ziggy3]

Ive had this cory for quite some time. Started out just his back fin was white at the very tip. Which has turned into what you see now over a span of months. he is housed with 5 other cories for his whole time i brought him home from the pet store, around 6-7 months ago. He eats fine. moves around like normal. i have a high PH of 8.0, and it stays consistent. ammonia 0. nitrite 0. nitrate 0.

Tank details
75 gallon
20 gallon wet dry sump
6 cories
5 discus
2 angels
Heavily planted (java fern, jungle val, anubius nana, amazon swords, wisteria, and crypt spiralis.)

Any help greatly appreciated.

P.S. he is the only fish like this.

 

[stanleo]

Ok the pH concerns me first. A pH that high is not really the best for all the fish you mentioned. They really should have a pH of 6.5 or lower. What is the KH and GH?

Also, your gravel is to rough for corys. They should have a sand or finer gravel than this. From the pics it looks like the cory has also lost its barbels which is what happens to them on that substrate.

I recommend changing the substrate to sand, a dark color, and frequent 50-75% water changes with dechlorinated water. If you have driftwood good but I would also add a few new pieces and more leaf litter without soaking them first. This will help lower the pH naturally. Also, if you do all this and the corys are doing better, up your school to ten or twelve and give more feeding of live or frozen protein. This will help elevate stress which will give his immune system a fighting chance.

 

[stanleo]

Also what is the temp? Juliis max out at 78F and that’s the minimum for discus.

 

[Colin_T]

it's either a protozoan infection or its skin is peeling off. If the skin is peeling off it would be something in the water but since none of the others have issues, I would go with protozoan infection.

Put the fish into a quarantine tank and treat it with something containing methylene blue and malachite green.
Make sure the medication is suitable for scaleless fishes, or if it isn't, only use it at half strength.

----------------------
wild Corydoras don't like a high pH but Juliis are usually captive bred, and the pH is not causing the issue.

 

[stanleo]

Yes it’s likely a protozoan. One of the many pathogens present in all freshwater systems that fish with a healthy immune system can fight off. Their immune system becomes compromised by stress that can result from being in a setup that is unsuited to their physiology. But yes, captive bred corys can tolerate a higher pH than there wild counterparts. But tolerate and thrive are two different things. There is an underlying cause to why this fish has become susceptible to a microbe that it’s immune system should be able to fight effectively and that’s what my comment was meant to address. And captive bred is a broad term. After enough generations of breeding in a higher pH the resulting generations become more tolerant but since there is no way of knowing how many generations this fish is removed from the wild or what pH those generations were bred in, erring on the side of “it needs a lower pH” makes sense.

But I am by no means an expert. I can only go by what I have read and experienced. I once had three sterbai corys in a setup with similar gravel to the picture in this thread and a pH of 7.4. One of the corys developed the same symptoms as this fish after a few months and died shortly after. Then another got the same symptoms. I searched high and low for the reason and came to the conclusion that the gravel and pH was the reason and switched to a finer gravel and lowered the pH to 6.4. It’s been almost four years and I still have the third sterbai ( he’s with 7 other corys now).

Also the statement “I know everything there is to know about fish keeping” has never been uttered by an aquarist, so I leave you with that and I hope things work for you.

 

[ziggy3]

To address everyone at one post.
Temp is at 80 degrees. i know it’s a little out of range for the cories but they seem to be fine with it. (i could be kidding myself)

GH and KH is unknown. i do not have a test kit for that.

I do have a mainly sand substrate. i have some gravel in there for looks. maybe ill start removing gravel. (All the cories still do have their barbells. it’s something i watch for)

I have well water, and i run a continuous drip system which changes 75% of my water weekly. and filter pad is changed once per week.

I guess i’ll try and quarantine this guy and medicate him to see how he does. its just weird that he is the only one.

Thanks for the replies, and any other comment/suggestions welcome. Just want to see this guy get better.