My betta fish has a swollen rear end. Is it bloated or sick?

Thanks for reaching out about Fred and including a picture. It is difficult to identify on the picture, but there is a small spherical red mass not he left lower body wall, that could be a wound, hypertrophic (enlarged) skin cell, or other concern (neoplasia). The recommendation is to monitor the mass for growth and if increases, seek an appointment with a veterinarian with experience in aquatics. Good luck.

Thanks for reaching out about Jeff and including photos. A swollen abdomen can be the accumulation of fluid, possibly due to diseases of the gills, heart, liver, lungs or something internal producing fluid. Sinking to the bottom, probably due to the fluid on the abdomen preventing the swim bladder from filling, therefore affecting buoyancy. First, test and correct water quality, as even small problems can lead to gill damage and the influx of water into the body, therefore the fluid. Adding non-iodized salt can decrease the water gradient into the body, relieving some symptoms but is not a cure. Salt from the pet store should have a dose. A veterinary visit is needed to assess if you want a more definitive answer. Good answer.

Thanks for reaching out about Bubbles and including a photo. Abdominal distention (often termed "dropsy") can be due to accumulated fluid, eggs, enlarged organs or displaced swim bladder. A veterinary visit is recommended to assess and provide a diagnostic/treatment plan. Store purchased medications are a waste of monies and will not fix anything. A diagnosis needs to be made to effectively treat. Good luck.

Yes, there are vets which would be willing to check him out but you should check that they are experienced and happy in treating fish ailments as not all vets would stock the correct medications or diagnostic equipments required for fish

Thanks for reaching out about Spike and including a photo. It is difficult to visualized the lump on the picture but if water quality is pristine, a veterinary visit might be in order to assess. Bumps/lumps can be parasites, infections, enlarged internal organs and more. Monitor appetite. Containers of food should be re-purchased every -23 months as vitamin C degrades quickly and fish has a nutritional requirement for vitamin C. If not a new fish (owned for several months or more), unlikely to be parasitic problem. Good luck.

Thanks for reaching out about Star. The abdomen can be distended due to multiple reasons. Constipation is one, but abdominal fluid, masses, swim bladder disease, are all possible. If eating and defecation, not constipated. A veterinary visit is recommended. Good luck.

Thanks for reaching out about Coco and including pictures. Swellings on one side of the body are often an indication of an internal mass. That could be a intestinal blockage, displaced swim bladder or an enlarged organ. Check water quality and correct any concerns. A veterinarian should be contacted for possible treatments, but also contacting the person/business you purchased her from would also be a good idea. This isn't much you can do for these problems at home. Good luck.