Hi,
I was very shocked yesterday when I went to feed my goldfish- all 3 were dead. I had missed feeding them for 1 day as I had been away, but I know that can’t be the problem as they can go a couple days without food. The situation in my tank is:
- got a goldfish starter set back about 6 or 7 months ago. Put 2 goldfish in there that I had in a bowl for a month before hand and they really enjoyed their new home
- about a month ago, I was away from home for a week and left my fish care to my mother – one of them died while I was away.
- I got 2 new goldfish last week to keep the one at home company. They all seemed to get along pretty well and were all active
- The day I brought them home I emptied all the water, added new water with conditioner. This has been my routine since I got my 2 original goldfish and never had issues. (I would do partial water changes periodically and full when the water got too dirty.)
- That day, I changed the filter sponge. I also added a new castle with a cave I had bought that day. I rinsed the castle with hot water as I know I can’t use soap. I rubbed the castle where I could reach to rinse off as much as possible.
- My orginal fish began to hide inside the castle after a couple days. I wondered about this and was a bit concerned, but I figured maybe he appreciated a nice quiet dark place. He would still come out for feedings.
- Then…yesterday happened. They were all dead. One of them had died inside the castle, one that I had never seen go in there.

I have 2 theories…but they all still have me wondering how they all died at the same time. I can understand more if one did…then a couple days later another…but I just don’t get how it all happened at once.
Theory 1- I didn’t quarentine the new goldfish. I got them from the same place as my other ones, and I was thinking about leaving them sepate for a couple days, but decided to just add them with my original fish
Theory 2- There was something in the castle that made them sick that I didn’t rinse off properly.

I would really love anyone’s guess at what might have happened and what i can do better. I am a bit nervous to get some new ones, and I probably won’t for a while. But I don’t want a repeat of this when I do decide its time to get some new fish.

Thanks in advance