I lost a Gourami last weekend, he had a dark and inflamed abdominal area. Sadly lost a hatchet fish today with the same swelling which was dark in colour. Anyone know what the problem is?
Have you noticed wether the scales are sticking out, I recently had a similar problem with a figher, It appeared to be dropsy, nasty horrible illness. Its very hard to treat successfully, but I would get some treatment for it and treat the tank. Any fish that develope the same syndrome should be taken out of the tank and put into a hospital tank.
Let me say though before I panic you to much, there are a number of causes for this such as constipation. What i would do Is try and identify as many symptoms of the fish as possible and then take a trip to your LFS and check the treatment containers, they will normally help you identify the problem and the best remedy for it.
Hope you sort it out, quite distressfull to both the keeper and the fish when things go wrong
How fast does the abdomen swell? If it's spreading from one fish to another it could be bacterial. Constipation can cause the same symptoms, have you changed food recently?