Tropical Fish Keeping - Aquarium fish care and resources

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busteds13 03-31-2008 09:43 PM

zit/cyst on cory's dorsal
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?

Falina 03-31-2008 10:00 PM

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?

Flashygrrl 04-01-2008 05:20 AM

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

okiemavis 04-01-2008 04:56 PM

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

-fish TB
-fish pox
-ulcer disease

busteds13 04-06-2008 05:47 PM

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

FrogHerder 12-18-2009 08:05 PM

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.

FrogHerder 12-19-2009 11:39 PM

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.

FrogHerder 12-23-2009 04:10 PM


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.

FrogHerder 12-26-2009 12:11 PM

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.

FrogHerder 12-27-2009 08:53 PM

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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