Goldie with sudden bruising

[Candiceg]

Came home from work today to find my young goldfish listless and with bruising along his dorsal fin both sides. Breathing heavy. Moved to a ten gallon and treating with marcaryn2 and aquarium salt. Has anyone seen this before?

[Autumnsky]

I had a fish which was having issues like this, JLK here on AA helped with excellent advice.

Do you have a water test kit? What are your parameters, Ammonia, Nitrites, Nitrates?

Do water changes, 50% then another 50%. Do you have a filter?

If it is the same experience I had, it is a critical situation.

Problems are worsened by poor water quality.

If you have a hang on the back filter, rinse the filter pad in tank water and then clean conditioned water, don't change the pad. Add an additional air pump or at least reduce the water level to increase oxygen for now. But probably will need additional air pump.

I was doing 50-75% water changes every day, mine got better but had two other episodes and it didn't eventually end up well.

I don't really have enough experience to give more help. Your fish may need medication and additional salt in the water to provide treatment.

[Candiceg]

Thanks for your help but he passed away last night. I'm just confused as to why this happened. One Sunday I did a 50% WC. And yesterday morning he was fine. When I came home he looked like this. Laying on the bottom with bruising on both sides. He was gasping gills swollen. I removed and put him in a hospital tank with marcaryn 2 and aq salt. I checked water in main tank and it was.
Ammonia .25
Nitrite 0
Nitrate 10 to15
Not sure where the ammonia came from but there is a dead leaf hanging on a plant in there. Still those readings shouldn't be enough to cause this. There are 2 other fancies in the tank and they seem fine. Any ideas what happened?