[Rinfish]

Substrate would cause the barbels to deteriorate. When I was more naive, I purchased flourite and eco-complete and my cories barbels suffered greatly and they were not thriving. I replaced it with Fluval Planted substrate (soft, circular granules) and they've grown back in two weeks.

The degredation of the barbels in combination with other factors (slightly unclean water, high nitrates, stressed fish as a result) may have caused a bacterial infection leading to lesions and rot. Can you take a picture of the injured cories?

Ultimately, I would put them in a medi-tank while you add the new substrate. Adding it while they're in the tank will be VERY stressful for them and they may be injured in the process. Use water from your tank to fill the smaller tank, then perhaps treat some of the water you usually add after a WC and fill the rest.

without more visuals I wouldn't feel comfortable diagnosing them. But there are antibiotics and antifungal medications available in chain stores (petco, petsmart).

Tetracycline and Maradin are antibiotics that will treat a wide spectrum of bacterial infections including rot.

API has a "Fungus Cure" that treats fungal infections + some secondary bacterial.

Look up beforehand which medications use copper, as Cories are very sensitive to it and could die if misused.

Googled an article and found this to be pretty helpful:

"Corydoras paleatus are very hardy and disease is not usually a problem in a well maintained aquarium. There is no guarantee that you won't have to deal with health problems or disease, but cory catfish are very resilient.

High nitrate levels can cause Peppered Cory catfish to develop infected barbels; this makes it difficult for them to navigate and eat normally. Maintain nitrate levels below 20 ppm through regular water changes. Because they are a scaleless fish, catfish can be treated with pimafix or melafix but should not be treated with potassium permanganate or copper based medications. Malachite green or formalin can be used at one half to one fourth the recommended dosage. All medications should be used with caution.

The best way to proactively prevent disease is to give your fish the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. A stressed fish will is more likely to acquire disease. Anything you add to your tank can bring disease with it. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so as not to add new diseases to the tank. For information about fish diseases and illnesses, see Aquarium Fish Diseases and Treatments."

Link is here: http://animal-world.com/encyclo/fresh/catfish/PepperedCorydoras.php

Hope this helps!

 

[Rinfish]

Additionally, a high-quality food will help boost the Cories immune system and make them happier overall! I just purchased Thera + "regular formula" to supplement my cories diet, and they are in LOVE with it.

Purchased it from here, but i'm sure you can find it in other places as well (though maybe not at a chain store.):

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=24616

 

[Rinfish]

I've ordered the new life spectrum thera+ a.

Thanks for the additional information. I was on a weekly water change schedule but I've

I managed to get a picture of the cory with the big lesion. I think it's gotten worse in the last couple days. Anyone recognize this or have suggestions for treatment?

Edit: ! was on a weekly 50% water change schedule, but the last couple weeks I have been doing it every 5 days.

oh goodness! Doing a bit of investigating, my suspicions are that it is Columnaris, or cotton-mouth. more info here: http://freshaquarium.about.com/cs/disease/p/columnaris.htm

without doing much research on medications, I would suggest Maracyn Two, as it is stronger then pimafix and melafix (which i have been reading does nothing to severe infections), and I think you need the strong stuff to reverse what is going on. =/

If you can, put him in a medical tank so you can focus on aiding him without messing up the main tank. a 5g would do nicely in this situation I think.

Good luck with your little guys!

Bump: In addition to everything, I might invest in some dried Catappa leaves or Banana leaves to help stave off infections and give your fish some stress relief. Its supplemental for sure, but it doesn't hurt to add a bit of extra!

 

[Rinfish]

Philip is right; poor water conditions do cause these sorts of issues more than anything. Even if substrate wont directly cause barbels to erode, if they are unpleasant for the fish that may induce stress or unhappiness which may in turn contribute to the formation of diseases caused by other factors, including poor water conditions.

I will say that my Cories are so, so much happier with the softer substrate I provided, with the same care and water changes I did prior.

Either way, perhaps some fish are pickier than others. You sound like you are very concerned for the well being of your fish so I am hoping and sending good thoughts to your little guys in hopes they pull through! If not, it is a lesson to know for next time so you can provide any future fish the best life possible.


Additionally: It may or may not be columnaris (its my educated guess), but the maracyn two would be able to give him a fighting chance, ideally.

To eradicate the bacteria in the main tank, I would add some aquarium salt (dose LESS than directed if your cories have not been exposed to it for a while, they are sensitive to salt), and keep up with the water changes like you are doing. Dose melafix as directed to promote healing and then, once all is said and done, buy some almond/banana leaves and let their antibacterial properties seal the deal (it'll help reduce fish stress as well).

My solution might be a bit pricey...but this is what I would do with my own tank. The water changes might eradicate it, but the melafix would at least help promote healing. If you want to go the cheaper route, do the water changes, add salt, and buy the leaves and see if those do the trick.

http://freshaquarium.about.com/od/termsandtables/g/mouthfungus.htm here is a website where you can buy leaves from. Have had good experiences purchasing products from him in the past.