What’s this swelling on my gourami’s face?
I've got a six-year-old kissing gourami which has developed a thick lip and swelling under the left eye. The swelling has come up over a couple of weeks and the gill doesn't close fully. There's no swelling on any other part of the body.
There was a big change in behaviour around 4-5 months ago. The gourami always used to be one of the first up for food and I could hand feed her; she had a big appetite and would also help herself to chunks of algae wafer. Since then, she's lost her appetite, just coming to the surface for a quick gulp of food and retreating. She's also had a couple of infections where the sides of her body developed several red blotches, but they went away with treatment.
The tank is a 360-litre freshwater aquarium, with a sand substrate and plants. Filtration is a Fluval FX4. I do a 20% to 50% water change every 7-10 days. It's been set up for around four years. Other tank mates are a honey gourami plus Congo tetras, harlequins, albino Corydoras, rummynose and black neon tetras, guppies and two bristlenose catfish. Water parameters all test normal. Please could you advise?
EMYR EVANS
PETER REPLIES:
We’ve pretty much ruled out physical trauma, such as a collision injury, given that the condition has developed over weeks rather than suddenly, and although you report outbreaks of infection in this fish, the lump and the mouth deformity with flaring of the gill plate doesn’t fit with classic signs of an internal bacteria or parasite infection.
In the absence of exploratory investigations, my ‘best-guess’ is some sort of tumour. These are caused by a genetic mutation in the fish’s cells, resulting in an uncontrolled growth of abnormal tissue. Such mutations can be hereditary or simply arise spontaneously, and some may be due to exposure to tumour-causing chemicals or tumour-causing viruses. Also, as fish reach old age, they become more susceptible to developing tumours. That said, your fish isn’t terribly old for a kissing gourami. I should stress that tumours in fish rarely imply bad fishkeeping—they just happen.
Tumours typically develop slowly over weeks or months, so this could explain the behavioural and physical deterioration you’ve observed in your gourami. A slowly enlarging tumour would account for the internal lump beneath the gourami’s eye, and the displacement of the mouth and flaring of the gill cover on that side.
You mention that the fish has had a couple of infections in recent months which were treated successfully. We know that certain types of tumours can make fish more prone to bacterial or fungal infections in particular.
If it is a tumour, unfortunately there isn’t much you can do. Some tumours, depending on their size, location and organ(s) affected, can be surgically removed by a specialist vet, but to be honest it’s not something I would consider in this case. One minor consolation is that tumours are not infectious.
I would simply continue to monitor the gourami and if the fish’s health deteriorates significantly or it stops feeding, you may have to consider euthanasia.