goldfish lying at bottom

I would like some ideas relatively quickly so I know what to do. My roughly year and a half year old calico fancy goldfish has been laying on the substrate in a specific corner of the tank, and I'm not sure why. When I tested my water on Friday evening everything was normal except for a slight...

Hi, my sisters goldfish has been lying at the bottom of the tank. He'll lie there for a few minutes then swim around for a few minutes then lie down again. I'm not really sure what type of goldfish he / she is, he has a body shaped like a common goldfish but patterns and a double tail like a...