Goldfish listless laying on bottom
Goldfish listless could be a multitude of issues. Ammonia, nitrite or nitrate poisoning could be to blame. Organ failure causes listlessness also. Unlikely the fish is old and dying, because most fish don’t live to a ripe old age
Oxygen deprivation causes the fish to panic, dart through the water, and to gasp at the surface. The gills redden. It will become listless if it’s dying however. Parasite infection causes flashing. The fish rubs and scratches on the substrate or tank decorations
In other words, the symptom listless needs a larger description. Does the fish have raised scales. Is the fish swollen. Is it eating.
The most important information to offer when asking for help with your fish is the water parameters. Test for ammonia, nitrites, nitrates, GH, KH and pH. Offer water temperature too. Tell the story; how long you’ve had the fish and how many. Describe their set up in detail. Describe the filtering system also
If you don’t know your water parameters; that’s okay. This tells a story in itself
Read and follow the 10 Steps to Goldfish Koi Keeping