Aquarium Polls

First Poll

What is your favorite brand of goldfish food?

TetraFin / Tetra
Other Brand

Current Results

Second Poll

What is your favorite type of goldfish?

Bubble Eye
Black Moor

Current Results

Fin Rot

Fish Fin and Tail Rot
fish tail rot
Torn ragged fins, maybe stuck together

anchor worm

Fin rot is often a symptom of disease and commonly plagues goldfish. It is not hard to treat fin rot and the outcome is usually positive. Fin rot is a symptom of a number of different diseases, but it can also be the result of an injury. It can be a primary or secondary infection. If it is primary it is a definite symptom of a specific bacterial invasion such as that by the mycobacterium that causes columnaris disease. Sometimes fin rot is the direct result of a secondary bacterial infection such as that which occurs when a goldfish is already weakened from another disease or following an injury.

fin rot goldfish

fin rot goldfish

Fin rot can be caused by a bacterial infection or a fungal infection. The bacterial infection results in a more ragged rotting while the fungal infection will rot the tail evenly and create a white edge.

When a whitish margin begins to appear at the edge of a torn or injured fin, a bacterial infection has probably taken hold. As the disease progresses, the fins rot away, eventually reaching the fin base and then into the body tissue itself. As diseased fin tissue dies, fungus often begins to grow on the dead areas. When that happens the white margin becomes inmistakable and may appear as a fuzzy, white, cottonlike edging.

The good news involving goldfish is that destroyed fin tissue can grow back if the damage does not reach the fin base. If , however the rot reaches the fin base, the goldfish will not be able to regenerate the damaged tissue. When the disease reaches the fin base , it may start to attack the goldfish body directly so the problem must be stopped before this happens.

Fish Medication - Mardel Tetracycline


Antibiotic that can be used to treat fin and tail rot, Popeye, secondary infections and gill disease. Primarily effective against gram-negative pathogenic bacterial diseases of fish. Symptoms of clamped fins, general listlessness, not eating or other unusual behavior can be caused by internal infections and treatment with Tetracycline would be indicated. Tetracycline is recommended for treating Popeye, gill disease, fin and tail rot and other secondary infections. Tetracycline is a broad-spectrum antibiotic that has been shown to be effective against a number of pathogenic bacteria associated with ornamental fish disease. Tetracycline may cause the water to turn red and a foam may collect on the water surface. It should not interfere with the biological filter. New activated carbon or charcoal and partial water changes after treatment will remove any remaining color as a result of the treatment. Available in tablet and powder form. Tablets and powder should be placed into the tank (not the filter). The tablets and powder dissolve and circulate through the water. For use in freshwater tanks only.

Strong goldfish that are in a healthy environment can sustain injuries and never show signs of fin rot. It is never wrong, however, to assume that an injured fish will become a victim of fin rot. Therefore it is not wrong to treat an injured fish for fin rot before the rot actually occurs. Doing such preventive treatment can help to head off the bacterial invasion that often will occur at the site of the injury.

The treatment is to do a major water change, adding aquarium salt , and making sure that you are providing a healthy balanced diet with plenty of vitamins. Medications should be added as the main treatment. Antibiotics such as tetracycline, chloramphenicol, or furance can be used if after a few days of salt treatment there are no signs of recovery.

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There are 15 comments
Posted by aimee – florida, usa

I have a fantail goldfish and his fins look roughed up and he lays on his side at the bottom of the tank part of his fin is missing could this be fin rot?

Posted by bri – az

my fantail callie appears to have fin rot on her tail and dorsel fin.her tail is splitting on the top and bottom ends.and her dorsel fin seems to be ripping off her tail is getting a reddish tint to it and she isnt moving much. is it fin rot and what should i do?please help!

Posted by sal – Mississippi

My female betta just developed fin rot. I called my aunt (she's a vet) and she is giving me some Tetracycline. What is the recommended dose for a 1/2 gallon tank? Also will acquarium salt help at all? Please help!

Posted by Sandy – San Francisco

I have a little two-inch girl goldfish named Spotty whose tail fins are fraying near the edges, now they're split about halfway in. There's maybe seven or eight separate frays, but no fungus except in a little hole higher up the tail. There is fraying on her left pectoral fin as well, and blackening on her tail and the fins near her anus (I forget what they're called). This is either China Disease or Fin Rot, but my parents won't let me buy treatment for the goldfish. Because they think it's only because she's in a six-gallon tank, but she's by herself and has three gallons per inch, as the two inches includes her not-so-pretty-anymore fantail. What to do?

Posted by Nykia – Sunderland, England

I had a goldfish not so long ago start to turn black a few weeks after I got her.. I was told not to worry. Then I started noticing her fins were torn and some was missing, I checked everywhere to see what it was and fin rot was the only explination. My mum said we'd get the medicine when I got back from summer school.. Sadly when I got back I found my other fish had died through a fungal infection and my mum had bought me 3 others. My little Masie was all fluffy.. I knew she wasn't gonna survive. So I focused on my new fish but the same is happening.. My white -with orange- goldfish has torn fins and doesn't eat much, she just lays there.. Is it time to administer the medicine before the disease progresses and she wont get better?
Please help!

Posted by Amber

Hey, I have 5 common goldfish and several are missing most to all of their fins. One is currently without all of it's fins, how it gets around is a mystery to me. Could this be fin rot?

One of my fish, my only gold one, has a longer tail than the rest. It's almost like a fantailed goldfish, but it's tail only seperates into two parts. Like if you held up your pointer and pinky fingers while keeping the others down. Is this a common gold fish or what?

Also, one of my fish looks like it's half blind. One eye has a 'star' in it. Any hints?

Oh, and I'm keeping my one and a half inch tutle in there with my three to four inch gold fish, is this okay? I have a 15 gallon tank, as my 55 gallon tank sprung a leak... =(

Posted by nazim – india

i bought 6 gold fishes 5 days back 1 lost at first day but others r now have problem with fins and i think they got infected with some kind of bacteria....
i used P. permagnate and salt today as i read this on some site. lets hope it ll work for them.

Reply to nazim
Posted by Shelly – California

Did it work? I have a goldfish that got fins torn on a decoration (which was pretty smooth but she somehow found the only way to get wedged into it, knocked it over, and tore her fins up:( ) Now, the smaller goldfish I have in the tank are biting at the "scabby" bits and making it worse. I've tried breaking their food regimen into smaller feedings more ofter and put more deco in to try and distract discourage this, but it doesn't work, and I suppose I'd better start cycling a recovery tank:( ! I haven't needed to use this sort of med in awhile and wanted to see if there were any new or improved formulations out there?

Posted by Lindzy – Jacksonville, Florida

I have 2 goldfish and one has been laying at the bottom of the tank for a couple days, he was always to most active so I did a partial water change and noticed the fin is torn away from his pectoral fin bone. It doesnt appear to be rotted but I added a container with salt to slowly despence into the tank. Will he recover from this injury? Does the fin gro back or reattach? he is a big guy and can only swim in circles so Im afraid he isnt getting enough food.
Thank you for any advice given!

Reply to Lindzy
Posted by elizabeth – charleston, sc

I have the exact same problem! It only looks like my fish is tired and less active but I to have noticed the same as you, that his tail is torn or part is missing. I think that the salt should work so good luck!!!

Posted by Hannah – Leander, Texas

My poor Betta fish died two days ago (May 14) because of this disease. He was just lying at the bottom of the tank not doing anything. I didn't notice it at all! He was a crowntail Betta, so he must've looked the same when the disease caught on. Rest in peace, Rae!

Posted by charlene – uk


Posted by Jhari – Ga, USA

thank you for this helpful article. It has been a looooong time since my fish have fallen I'll so when one did, I found myself a bit panicy and forgetful of what to do. Thankfully this article put me at ease and I can medicate my ryukins with peace of mind. Thanks!

Posted by ahmer – Bangladesh

i have also lost my 4 orandas and 1 of my most fav fish for the disease..all the fins got torn .but i couldn`t help the there any more ways of medicine without parchasing medicines.

Posted by Rob – Australia, Sytdney

Ive lost about 5 fish already to fin rot, the main fin that runs along the top of one of my fish is torn between each divide and the fish has lost 30% of its scales... does he still have a chance???