# zit/cyst on cory's dorsal



## busteds13 (Feb 18, 2008)

so i just noticed this morning that an emerald cory in my tank has this yellowish zit/cyst-like growth on the back of the base of its dorsal fin. he also looks just a little bit bloated. all other fish appear fine, and he's not acting strange. any ideas?


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## Falina (Feb 25, 2007)

Could you post a photo? This would be the best help we could get in order to in turn help you identify the problem.

What are your water parameters?


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## Flashygrrl (Jan 18, 2008)

I'd suggest going through the diseases sticky and seeing if you can find it


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## okiemavis (Nov 10, 2007)

Here's the top causes, why don't you check them out and see what matches up?

-fish TB
-fish pox
-lymphocystis
-ulcer disease


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## busteds13 (Feb 18, 2008)

alright, here's a picture and a short video. both are a little fuzzy, but i think the video gets the point across. 










http://www.youtube.com/watch?v=ZY6p2AUf-YI


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## FrogHerder (Dec 18, 2009)

Hello all,

New to the forum. Our Emerald Cory is having the exact same problem. Oblong oval cyst-looking thing at the rear base of the dorsal fin. Were you able to figure out what was going on with yours busteds13?

Does anyone else have a good idea what this might be? 

We have quarantined him in a little hospital tank, and have been treating with Wardley's Ick Away/daily 50% water changes for most of a week. No results yet. If anything, it's gotten slightly larger. I can tell it's starting to become a bother to him. Hope we can get it figured out and treat whatever it is in time.

Any help would be appreciated.


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## FrogHerder (Dec 18, 2009)

OK. So after reading through the diseases sticky, and spending hours and HOURS online here and other places, I've come to the conclusion that our little Cory likely has a mycobacterial infection (Piscine TB).

We have a 6-gallon Marineland setup with biowheel and cartridge filter. Probably at the upper limit of what should be living in it. 

4 Harlequin Rasoboras (approx 1-1/2")
1 Otocinclus (approx 1-1/4")
2 African Dwarf Aquatic Frogs (one male and one female)
1 Emerald Corydoras (now quarantined in a 1.5 gal hospital tank)

We are fairly fastidious about water changes. 25% once a week with a gravel vacuum. The aquarium is heavily planted to help keep the oxygen levels up, and the nutrients under control.

Temp is fairly steady around 78 deg F. Nitrates always read in the "safe" zone with our test strips. Nitrates, chlorine, and ammonia are always too low to register. We keep the pH a little on the high side for the frogs. 7.2-7.4.

Anyways - back to the TB. We had the frogs previous to getting the aquarium. They were a gift from a well-meaning relative. After about a week it was obvious the tank they came in was just not adequate for them, so we bought a nice 6 gal Marineland setup. We bought some live substrate and planted it. We let the tank sit for a week, and watched the chemistry to make sure it was stable before adding the frogs. Decided to add 4 Harlequins to the two frogs for some eye candy. The frogs are not always active/visible. 

One of the 4 Harlequins died about 3 days after coming home with us. No warning. Went to bed - he was fine - woke up and he was stuck to the filter intake. Took it back to the pet store with a sample of our water. The store attendant said the nitrites maybe looked a little high. Took our replacement fish home, and tested the water before introducing him. It looked fine (nitrites did not register).

Everything was fine for a month. Started having some algae buildup and were worried about it building up on the leaves of the live plants, and so brought an Otocinclus and a Spotted Cory home. That Cory got very ill the next day. He seemed weak, was having equilibrium problems, and the area around his mouth turned red. We took him back to the store before he passed (with a sample of water). The attendant checked the water, and everything was great. She said the Cory maybe had some kind of parasite that caused it to hemmorhage internally. Seemed plausible enough. They said they would stop selling fish from that tank temporarily and tag it for observation. Accepted the Emerald Cory as a replacement from another tank. 

Two months with no issues until the Cory started to develop a growth identical to the one in the picture put up by the original poster.

I know the disease sticky thread states that treating is not practical for fish TB, and the fish should be euthanized. Not comfortable with that. There is no practical way to POSITIVELY ID the problem as mycobacteriosis. There are also other family members even more sentimental than I am about the fish. (The frogs are my babies, and I am sure as hell not going to off them even if they start showing clinical signs). 

Going to stop treating with Wardley's as it has had no effect, and is not really good for bacteria. Came across some info that it may be possible to knock the infection back to sub-clinical with Kanamycin and Vitamin B-6. Will post occasional progress reports. If nothing else, maybe someone else with the same problem can learn from our experience.


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## FrogHerder (Dec 18, 2009)

Update:

One of our 4 Rasboras became ill 3 days ago (bloating on one side, equilibrium problems, and pop eye), and has been moved to the hospital with the Cory. 

Apparently there are several other bacterial infections that can present with the same symptoms as mycobacterium marinum including pseudomonas, aeromonas, and streptococcus. Glad I didn't euthanize, as the others are fairly treatable.

Was unable to locate Kanamycin locally. Picked up some Jungle brand medicated food (sulfa drugs, I think) and erithromycin powder from a local pet store. Had some trouble getting the fish to take the food at first, as the pellets were too big for them. Crushed them to a powder between two spoons, and now they are eating it up. They don't seem to miss their flake food. Have been treating the fish in both the hosp tank, and the home tank for 3 days. Also using melafix in the hosp tank (figure it can't hurt). 

Not using melafix in the home tank as I am unsure if it will irritate the frogs' skin. Have been mixing some of the erithromycin into the thawed brine shrimp and bloodworms for the frogs. Not sure who was the original vector for the bacteria, so we are treating EVERYONE.

Doing 25% water changes in the home tank and 50% in the hosp tank every other day. I'm sure all our BB are dead, so I've been checking the chemistry at least once per day.

Some good news. The cyst on the Cory's fin is noticably smaller, now. It has shrunk from approx 1mm x 2mm in size to 1/2mm x 1/2 mm. The Harlequin in the hosp tank is also doing much better. Still a small amount of bloating, but the pop eye is back to normal size, and the swimming problem is gone. He doesn't seem to be eating much, though.

Some bad news. The Cory has another tiny cyst on his nose. Has been there for about 2 days. Not changing in size or appearance.


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## FrogHerder (Dec 18, 2009)

Things are really looking up for our two sick fish. The cyst continued to shrink down to a withered little sac yesterday. This morning all remnants of the cyst and the white spot on his nose are COMPLETELY GONE. :-D The rasbora is doing much better, also. The signs of dropsy are going away. No pop eye in a couple days, and the bloating is noticably better this morning.

This is one full week after starting treatment with the Jungle brand anti-bacterial food and API erithromycin powder. Will continue to QT/treat them for a couple more weeks as a precaution.


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## FrogHerder (Dec 18, 2009)

Don't even know if anyone is reading this, but it may be a resource if someone else's Cory gets sick like ours.

Today's update - the Otocinclus in our home tank passed. 2nd one in as many months. There is a small amount of green algae visible on the aquarium sides. Don't think it was starvation. Could have been stress from the antibiotics or constant water changes. Also could have been rough treatment from our female African Dwarf Frog. She sometimes nips at the fish if she thinks they're too close to her food. 

Now changing 1/3 of the water daily to control the ammonia levels as all the beneficial bactera are obviously dead. Removed the dead oto from the tank, and cleaned the net with bleach solution after.

We are going to be setting up a larger tank for the frogs. Going with a 10 gal for them and the rasboras. The 6 gal will house a betta that is now living in a 1.5 gal tank. The Cory will also be going in there if/when we feel he's cured of the bacterial infection.

The Cory's dorsal fin is still looking good. Just a small opaque patch where the cyst used to be. His nose is about the same. Will begin treating with Kanmycin in addition to the Erithromycin and anti-bacterial food as soon as we are able to locate that product. The pet stores don't carry it, and neither did the aquarium shop that sold us the frogs. Will try some pond supply stores.


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## Mean Harri (Dec 14, 2009)

Wow, what a battle. I do know from reading that UV sterilizers can help with a lot of bacterial infections. They can also help with fish TB in that the TB weakens the immune system making the fish more susceptible to other diseases. And the UV sterilizer can kill these bacteria that would otherwise infect a fish with a weakened immune system.

Fish TB is a huge problem. Or at least was. I did some reading from 2006 information. I do not know if things in the industry have improved since then or not. Google "Diana's diseased fish" those 3 words. lots of good reading.


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## FrogHerder (Dec 18, 2009)

Thanks for the link, Harri.

Good reading. Fish keeping sure has changed since I was a kid. Kept Bettas, Cories, Crawdads, and what have you with no problems other than the occasional fish jumping out of a cup during major tank cleanings. 

The Cory still has the small white lesion on his nose. We found some tetracyclene in gel-food form at another LFS. It's a broad-spectrum drug, and supposed to be effective at killing mycobacteria. Hopefully he will eat it. Have had no luck whatsoever finding Kanmycin (sp?) locally. We're going to keep treating him with antibiotics for probably another couple weeks. At that point, the hospital tank will probably become a hospice tank for him and the harlequin rasbora with the bloat problem. We'll add a little soft sand and probably a plant, and try to make them comfortable as possible. Will keep some clove-oil on hand in case it looks like they're obviously suffering. Who knows, if we quit doing 50% WC every other day, and give him some soft sand and real food, the Cory's little nose just might heal by itself? (I can hope, right?)

We have treated the other tank with the healthy fish and frogs aggressively with antibiotics for a couple weeks, and none of them are showing signs of illness. We purchased a new 20g long aquarium for these. The tank is set up, and we are waiting for the BB to build up (doing a fishless cycle) before we transfer them over. We wanted a bigger tank, as we were concerned that crowding may have played a role in the fish getting sick. The expense of the new aquarium along with the cost of the medications for the sick fish has us pretty well tapped-out. If we do get a UV sterilizer, it will have to wait a couple months.

If everything keeps dying off, we will probably just go scorched-earth, bleach-bomb EVERYTHING and start over. Sometimes that's the way things go in life. Will be MUCH more particular in the future about where we buy fish from. As an aside - there is a seahorse breeder (forgot the name) that has their operation certified as SPF ("Specifically Pathogen Free") for mycobacteria marinum. Will have to check around to see if I can locate fish breeders who also go the extra mile. The peace of mind would be well worth paying double or triple the price for healthy stock.


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## FrogHerder (Dec 18, 2009)

Located an _excellent_ paper on M. marinum published by Iowa State University. 

http://www.cfsph.iastate.edu/Factsheets/pdfs/mycobacterium_marinum.pdf


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## FrogHerder (Dec 18, 2009)

Got a UV sterilizer for the new tank. Got some christmas money from a relative, and were able to afford it. They really don't make anything small enough for the hospital tank.


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## FrogHerder (Dec 18, 2009)

Apparently I like talking to myself. :roll:

Anyway - treated the Cory for 3 weeks with erithromycin and Jungle antibacterial food. The cyst went away quickly and has not returned. That area on his dorsal now looks completely normal. The white spot on its nose is still there. The rasbora is doing great. No outward signs of illness. Slightly pudgy - and has been the entire 3 months we've had it. Obvious bloat is gone.

As the white spot is still there despite the antibiotics, we're going to treat it as fungal for now. Added play sand to the bottom of the hospital tank. The cory seems soooooo happy to have something to root around in. I'm hoping it will help debride/heal the area and may help with working the meds into the wound. Treating with API antifungal (the tank water looks like gatorade, but the fish seems fine with it).

A little about myself - I have a degree in biology and worked for the fisheries dept of our state wildlife agency when I was in school. Unfortunately, most of my experience involves electroshock surveys and Whirling Disease inventories in the wild. _*Not*_ helpful to mister cory cat. I know a _little_ about diseases and how to recognize them but - I AM NOT A VET. 

Feeling really helpless right now - I've always felt very responsible for any animals I bring into my home. Would anyone with good experience/expertise dealing with sick tropicals be willing to chime in?


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## Byron (Mar 7, 2009)

I've read this thread, but as I have extremely minimal knowledge of disease issues I tend not to get involved and leave it for those who have such knowledge, and there are several here who do but perhaps over the holidays they haven't been active online.

My comment is for the future to keep your cory healthy; he needs some companions. I realize this is a 6g tank, but corydoras are shoaling fish and very social; 3 would be ideal. And if you keep up good maintenance I would sooner have 2 more corys than not. And being heavily-planted is a bonus; plants are incredible water filters. 

I really do recommend two more Corydoras aeneus, or another species if you'd prefer variety, as corys generally shoal together when different species. Make sure they are Corydoras aeneus and not Brochis splendens, a fish that looks almost identical but grows larger. You have Corydoras aeneus if it looks like the fish in the original photo; the dorsal fin has 7 rays as all Corydoras have, whereas Brochis splendens has 10-12 rays.

Byron.


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## FrogHerder (Dec 18, 2009)

Thx for the advice on keeping more than one cory. Byron. The hospital tank is just a 2 gal. Our betta now calls the 6 gal home. Was just given a moderately neglected 40 gal (whole nother story ) and that is where cory cat will end up if/when we're reasonably sure he's not a danger to make the other residents sick. There is already one other cory there (unsure of the sp.) and plans to add more.

A little tough to count because he's moving around so much now, but I broke out a magnifying glass, and the fish appears to have 8 dorsal rays (branched), not counting the barb at the leading edge. Is it a mutant? :shock:

I looked at some pictures of aeneus, and he does appear to be one (other than the extra ray). So I was mistakenly calling it an emerald cory, when apparently it is a bronze cory? They can take in oxygen through their intestines? Wow. Saw some bubbling action at the vent a few days back, and just assumed it was flatulence :lol:. I guess there's a chance that 'he' is a 'she'. How does one sex them (other than breeding behavior)?

Anyway, the lesion appears to be getting better. Another 48 hrs left on the antifungal treatment and then maybe-hopefully done throwing meds at him.


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## Byron (Mar 7, 2009)

FrogHerder said:


> Thx for the advice on keeping more than one cory. Byron. The hospital tank is just a 2 gal. Our betta now calls the 6 gal home. Was just given a moderately neglected 40 gal (whole nother story ) and that is where cory cat will end up if/when we're reasonably sure he's not a danger to make the other residents sick. There is already one other cory there (unsure of the sp.) and plans to add more.
> 
> A little tough to count because he's moving around so much now, but I broke out a magnifying glass, and the fish appears to have 8 dorsal rays (branched), not counting the barb at the leading edge. Is it a mutant? :shock:
> 
> ...


I went back to Burgess to check this out, and he writes that Corydoras have 6-8 rays in the dorsal. The three Brochis species have 10-17, with B. splendens having 10-12 which is the fewest of the Brochis species. Brochis are usually obvious, the dorsal fin extends a fair length along the dorsal ridge and the last ray is very close to the adipose fin quite unlike the Corydoras.

Common names can be very misleading. Corydoras aeneus is seen in stores as bronze cory, green cory, emerald cory, "cory", etc. Always know what you're buying. Good fish stores usually have reference books on hand, and if they do won't mind you looking up something you see and don't know about. I've a tremendous interest in South American fish, especially characins and the Callichthyidae (Aspidoras, Brochis and Corydoras) but I still see fish I don't know especially now that collectors are entering remote areas previously un-fished and finding new species that sometimes get to the store before they are named. I have a group of characins in my 115g that to my knowledge have not yet been scientifically described and named. They appear to be a species of Hyphessobrycon or Hemigrammus; they came direct to one of my local stores from the collector in Peru who happened to find them and decided to export some.

I have only been able to sex mature Corydoras by the girth of the female which is quite obvious. Sometimes spawning or pre-spawning behaviour is a clue, the way the male positions himself crosswise in front of the female. To my knowledge there are no external sex differences in colour or pattern. Glaser says that the pectoral fin ray of the male is thicker when viewed from above.

The ability/need to "breathe" air is quite remarkable. All species in the Callichthyidae (and many other catfish too, like otos) must periodically and regularly swallow a gulp of air which then passes to the hind gut where blood vessels take up oxygen before the air is expelled. If the fish is prevented from doing this, say by a tank with a glass cover at the water surface so no air is available, the fish will literally drown. Similar to the anabantids with their labyrinth organ. There are clear biological reasons for these adaptations. The Callichthyidae are able to live in oxygen-poor water and some even in basically mud because of this feature. Nature is remarkable.

Byron.


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## FrogHerder (Dec 18, 2009)

Thought _for sure _we had killed the cory with kindness yesterday. The API Fungus Cure turned the water a special shade of radioactive green, and the little guy seemed to be wearing down from all the meds. Wasn't really eating much, and while I wouldn't say its fins were exactly 'clamped' they weren't splayed in the usual manner either. Very sluggish and did not eat a bloodworm that was offered. Overall, the fish just seemed depressed and I thought there was about a 50/50 chance it would go belly-up overnight.

Did a 50% wc last night, and put a filter cartridge with some carbon in. Woke up to some very encouraging signs. The white patch on the cory's nose is GONE. It's behavior is also much better. Positively pigged-out at feeding time this morning. Back to being the same hyperactive, expressive little fish we brought home 3 mos ago. The only thing left 'wrong' is a very small amount of erosion on the lower half of its tail fin. That has been there unchanged for 5 weeks, and_ may_ have been there the entire time we've had the fish. 

The carbon seems to have neutralized most of what meds were left in the tank after the wc. Going to keep 'Blinky' the cory, and his (her?) buddy the harlequin rasbora in the QT (and continue 50% wc every other day) for at least another week or two and watch very closely for any sign of sickness. My gut feeling now is that this was not a myco infection, but something else. I realize that could be wishful thinking, which is why the fish will be staying in QT for now without meds and observed very closely.


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## Byron (Mar 7, 2009)

FrogHerder said:


> Thought _for sure _we had killed the cory with kindness yesterday. The API Fungus Cure turned the water a special shade of radioactive green, and the little guy seemed to be wearing down from all the meds. Wasn't really eating much, and while I wouldn't say its fins were exactly 'clamped' they weren't splayed in the usual manner either. Very sluggish and did not eat a bloodworm that was offered. Overall, the fish just seemed depressed and I thought there was about a 50/50 chance it would go belly-up overnight.
> 
> Did a 50% wc last night, and put a filter cartridge with some carbon in. Woke up to some very encouraging signs. The white patch on the cory's nose is GONE. It's behavior is also much better. Positively pigged-out at feeding time this morning. Back to being the same hyperactive, expressive little fish we brought home 3 mos ago. The only thing left 'wrong' is a very small amount of erosion on the lower half of its tail fin. That has been there unchanged for 5 weeks, and_ may_ have been there the entire time we've had the fish.
> 
> The carbon seems to have neutralized most of what meds were left in the tank after the wc. Going to keep 'Blinky' the cory, and his (her?) buddy the harlequin rasbora in the QT (and continue 50% wc every other day) for at least another week or two and watch very closely for any sign of sickness. My gut feeling now is that this was not a myco infection, but something else. I realize that could be wishful thinking, which is why the fish will be staying in QT for now without meds and observed very closely.


Some good actions noted here, well done. Keeping in QT is fine, and without any medication is very sensible with Corydoras, as I'll explain momentarily; connected to this is the fact that the pwc almost certainly saved the cory's life.

I have learned from experience over 15 years that Corydoras are extremely sensitive fish to chemicals, salt, medications, water parameter changes and water quality problems. Characins as a group are probably second in line, but Corydoras are at the top of the list. I no longer treat aquaria containing Corydoras unless it seems absolutely essential to save the fish. I have observed the exact same reactions in corys as you describe, from several different medications; the first sign has always been very increased respiration, then eratic movement, then sluggishness to the point of death. When treatment is deemed essential, I now observe the corys and am ready to do a major pwc every day if necessary.

The green is likely malachite green and/or acriflavin, both highly toxic to these fish if prolonged or in strong dosage. As for the tail fin, it may grow back; torn and missing fins usually do, though not always.

Byron.


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## FrogHerder (Dec 18, 2009)

Byron said:


> Some good actions noted here, well done. Keeping in QT is fine, and without any medication is very sensible with Corydoras, as I'll explain momentarily; connected to this is the fact that the pwc almost certainly saved the cory's life.
> 
> I have learned from experience over 15 years that Corydoras are extremely sensitive fish to chemicals, salt, medications, water parameter changes and water quality problems. Characins as a group are probably second in line, but Corydoras are at the top of the list. I no longer treat aquaria containing Corydoras unless it seems absolutely essential to save the fish. I have observed the exact same reactions in corys as you describe, from several different medications; the first sign has always been very increased respiration, then eratic movement, then sluggishness to the point of death. When treatment is deemed essential, I now observe the corys and am ready to do a major pwc every day if necessary.
> 
> ...


Thank you for the heads up on corys being sensitive to those meds, Byron.

Hopefully this will be my final update to this thread.

Both quarantined fish showed no further signs of illness, and have been added to stocked/cycled tanks. In my last post, I stated that I did not believe this to be a case of myco. Main reason being that I have no veterinary skill and did not have the meds the experts advise to use for myco, and still both fish are alive and well. The cory's dorsal fin was obviously some type of bacterial infection, but healed quickly after administering common antibiotics. The nose was probably just something it did to itself after going into QT (rubbed raw) and got a fungal infection. I believe the harlequin may have just had a swim bladder infection (or possibly early dropsy), but also made a quick recovery. No other fish in the house have come down ill.

The cory was added to our 40 gal and has become fast friends with the unknown cory that came with the tank. If you're reading this, Byron, I was wondering if you'd be willing to take a shot at ID'ing the cory pictured in my aquarium pics?


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## Byron (Mar 7, 2009)

FrogHerder said:


> Thank you for the heads up on corys being sensitive to those meds, Byron.
> 
> Hopefully this will be my final update to this thread.
> 
> ...


If it's the cory in the 40g photo, it is Corydoras paleatus, common name usually peppered cory. This was the first corydoras species I ever kept, decades ago now. There is also a high-fin variant (extended dorsal fin). Quite a nice little cory. B.


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