View Full Version : Lump behind the gill opercle

11-14-2009, 10:19 AM

My Comet type goldfish has a lump behind its left gill opercle. It already had this problem in September, but after one week, the lump disappeared. It came back 2 weeks ago.

My fish's behavior and appetite haven't changed at all. It eats well (Gold Japan pellets or Artemia in the morning; boiled vegetables or Tetra Plecomin with spirulina in the evening) and is still active.

Here is a tentative picture taken 2 weeks ago:

You can see the lump. It is a bit whitish and the scales seem bigger there.


I am a bit puzzled because it doesn't correspond to anything I could find on the Web. After 15 days, the lump seems a bit more whitish, but it hasn't grown any bigger. It is stable.

I hope you can give me a clue as to what this is.
As a cat breeder, I know that you mustn't treat an animal unless there is a very good reason to do so, and that the stress undergone during a treatment could be worse than the problem itself, which is why I haven't attempted anything yet. My fish doesn't seem to be suffering and I'd like to understand what is going on.

My tank is a 14g one. It has been running since July 24th.
The following water parameters were taken today:

PH = 8
NO2 = 0
NH3 = 0
GH = 12
KH = 8
NO3 = between 12.5 and 25 mg/l
Temperature = 21C (69.8F)

I use a Tetra test kit for PH/NO2/ NO3/GH/KH but a Sera test for NH3.

This tank's filter is a TetraTec 400 cannister filter (105g/hour); it has been in use since October 4th (I had an internal filter before but it broke down). I rinse the Perlon or the sponges every 10-15 days I change the tank's water twice per week (30%) and I use a TetraTec GC30 gravel cleaner to perform the water changes. I also use some Tetra Aquasafe water conditionner to change the water (always at room temperature).

There is no substrate in this tank but only river gravel. There is just one fish : a Comet type goldfish with 7 ramshorn snails, and 3 melanoid snails.
My fish must be around 2 inches long, without the caudal. It is a rescued fish and I have had it since July 3rd, 2009. It must be around 2 years old and has always lived on its own.

It will soon be transfered into a 30g tank which is actually cycling.

Thank you for your help.

All the best from France,


11-15-2009, 04:24 PM
All I can tell from the pic is that the skin near the left gill appears raised from the frontal view. It's too difficult to try to speculate the cause. It's probably not tumor if it comes and goes. Possible chronic infection with occasional flares, but who knows.

Personally, I'd leave it alone if the size of the lump has not progressed.

11-15-2009, 05:50 PM
Thank you for your answer and advice, Suphi.

If it is an infection, I hope it doesn't spread. This is what I'm worried about.

12-26-2009, 06:12 PM
I'd like to give you some news of my goldfish and its lump. Alas, the lump hasn't gone away - quite the contrary actually, as it has grown a bit more. The evolution is slow nonetheless. My fish's behavior is still the same.




Cincy Ranchu
12-27-2009, 02:00 AM
These pictures appear to be a cyst or tumor. My experience is that it is not contageous.
The only treatment I can suggest is lyse with a needle squeeze it out and dab with an antibiobiotic cream like neosporum.

The other alternative is removal, the sugery will prolong its' life and is not very difficult

12-27-2009, 07:13 AM
Thank you for your answer, Cincy Ranchu. The lump indeed appears to be full of liquid. Maybe I should try the surgery if it can help on a long term basis. If there is something to be done, I'd like to give it a try.
Could you tell me how to proceed?

12-27-2009, 01:19 PM
Stick a needle in there (25G). If it's a cyst then it'll decompress and you can drain the fluid inside. If it a tumor it'll stay the same. I'd probably leave tumor alone, though.

This should be done in a tub and fish should probably be anesthetize first (clove oil, you can google it).

Looking at the latest photos, that lesion seems like a solid mass to me instead of a cyst...but you'll never know for sure unless you stick it with a needle.

12-27-2009, 11:55 PM
OK, Thank you Sushi. I'll try to find the required equipment to deal with the cyst/ tumor (needle, clove oil, antibiotoc cream to avoid surinfection).

12-28-2009, 04:22 AM
The cyst will usually come back a few months later.


01-01-2010, 09:54 PM
Look up lymphocystis on internet search. The more I think about it the more I'm incline to say this may be the problem.


01-02-2010, 09:37 PM
It is an interesting link. Thank you, Suphi. :)

01-21-2010, 05:28 PM
You were right: the lump is a tumour. There was no liquid inside but just flesh and blood.
I asked my vet to have a look.

What should I do to avoid an infection at the site of the sample my vet took?

I couldn't find the neosporum cream. Would salt bath be enough?

01-21-2010, 06:36 PM
Just keep the water clean and observe. If the fish is healthy you don't need to do anything else. Animals typically have better immune system than us. Salt will not touch bacteria or fungal infection so there's no need.

01-21-2010, 08:09 PM
OK, thank you Suphi.

My vet is researching the procedure to remove the tumour. He said it is superficial and he's willing to perform the surgery.