Fish Staying At The Bottom Of Tank. Check for ripped fins, hiding fish, or fish that seem to be. That will be the easiest way to diagnose what the problem is.

But fish that have long fins can end up spending a lot of time at the bottom because fins weigh them down. There has to be some sleep time, for fish in your aquarium and since they don't close their eyes and lay down it's a little difficult to know when they do it. Your goldfish may also develop sores on the bottom of the stomach if the rough substrate is cutting into their scales the whole time.