What’s causing this bloating?
I have six Silver Dollars in my tank, and they have given me no issues at all for the last couple of years, but I’ve noticed that one of them has become very bloated recently. It hasn’t really affected the fish’s swimming, but it doesn’t seem to be feeding very much. Any advice would be appreciated. BRYAN TONG, VIA EMAIL
PETER REPLIES:
Bloating is typically caused by an accumulation of fluid within the fish’s tissues. In some cases, the bloating may be accompanied by scale erection, giving the fish’s body surface a ‘pine-cone’ appearance and/or pop-eye (also known as exophthalmia).
Bloating is generally the result of some sort of damage to the fish’s kidneys or other organs involved in osmoregulation. Often, a bacterial or viral infection is responsible for the organ damage, but in some cases organ failure due simply to old age may be to blame.
I should add that certain internal tumours can also cause a gradual swelling of the body, and female fish can also swell up with eggs (or fry). But it sounds from your account that the bloating has occurred fairly quickly — probably over days, rather than weeks — in which case a tumour is a less likely cause.
Bloating can be difficult to treat, but I’d try an anti-bacteria remedy from the aquarium store in the hope it’s a bacterial infection (viral infections, by contrast, are untreatable). But even if bacteria are to blame, be aware that over-the-counter remedies don’t always work in dealing with internal bacterial infections, and the alternative would be a trip to your vet to see if antibiotics could help.
If you can isolate the fish for the duration of treatment, so much the better, as this avoids exposing your other healthy fish to the medication. And if you can house your affected Silver dollar in an isolation tank, try also adding some salt (sodium chloride), at 2g per litre, as this can help reduce osmotic imbalance. Most anti-bacterial remedies can be used in conjunction with salt, but always check the manufacturer’s instructions just to be sure.