My friends Goldfish died, and she said their stomach turned brown?

Question

What could be the cause of this, she cleans the bowl every week?

Answer 1

It sounds like velvet. Velvet is similar to ich in looks but usually only when magnified. There are little tiny goldish brown specks that can usually be seen when under a magnifying glass or if you shine a light into the tank.

Most fish disease is caused by weakened immune systems. Regardless if she cleans a bowl every week or not, her fish will be stressed. You mention "their" but not how many. Each goldfish requires a 10 gallon upgrade in tank: 1 fish, 10 gallon tank, 2 fish, 20 gallon tank, etc. When kept properly, goldfish can get up to 10" and live for 20 - 30 yrs.

They put out a HUGE amount of waste and without a really good filter system, they have been swimming in a ton of ammonia. Ammonia appears in fish urine, feces, decaying food matter (they're sloppy eaters) and even in the exhaling of used oxygen from their gills. Usually, it's recommended you get one size filter up from the size of tank just to handle the heavy bioload. So if she had two goldfish, she should have had a 20 gallon tank with a filter system for a 30 gallon tank minimum.

Answer 2

Velvet can certainly cause a brownish appearance on a fish, but usually all over not just in one area. I would say other options include ammonia poisoning / burns. If your friend had several goldfish in a bowl, ammonia would build up very quickly and she would need o clean the bowl every 1-2 days to prevent problems.

If she can, a 20 gallon tank would be a good home for 2-3 gold fish until they grow larger when it's best to have only one even in a 20 gallon tank. If she wants to stay with a bowl, her best bet is a betta and even then she will need to change all of the water and clean the bowl every 2-3 days.

MM