Why do your goldfish stay in a group at a corner?

Answer 1

Goldfish need colder water, so it's likely that the corner they're in is cooler than the rest of the tank, or they're in a spot that has a higher rater of water flow from the filter, which would also make it cooler. If the corner they're schooling in is at the low point of the tank, the cooler water theory fits since cooler water is at the bottom.

However....

If they're in a corner at the top of the tank, they might not be getting enough oxygen. Oxygen content is replenished at the water surface, and how well the surface is being agitated determines how much the fish will get. In nature, fish in ponds get oxygen when the surface is agitated by wind or rain - in a river or stream, it's the current that does it. In a fish tank, filters are designed to agitate the surface of the water, and that's also the real function of air stones. In an undergravel filter, the air stones perform 2 functions - draw waste material into the stones (which acts as the filter medium where bacteria break it down) and to break the surface tension of the water with the air bubbles.

To really find out what's going on in your tank, you should have an Ammonia test kit and a Nitrate test kit, as well as a PH kit. Knowing the quality of your water is the biggest clue as to why your fish may be behaving abnormally. They don't cost much when compared with the ridiculous prices for fish charged by places these days.

Answer 2

Not typically, as they are really not a schooling or shoaling fish. Often if they huddle at the bottom, they may be resting, their water may be too cold for them to feel comfortable, or there is a water quality issue due to increased toxins which can be helped with regular water changes

Answer 3

Not sure. But I just know that their memory span is 3 seconds. So maybe they're like: "I forgot to explore this side of the tank." Just a joke.

Answer 4

they follow each other