Moving a goldfish is a logistics problem disguised as a fish problem. Goldfish are large-bodied, breathe hard, and produce waste at a rate tropical fish never approach, so every part of the plan, container size, water volume, fasting, filtration at the far end, has to be scaled up. Owners who move goldfish in fish bags learn this the hard way; owners who move them like the small livestock they are find the day almost dull.
Respect the waste and the oxygen
Fast your goldfish for a day or two before moving day, longer than you would fast a tropical fish. A goldfish digesting food in a sealed tub is steadily filling a limited volume with ammonia, and an empty gut is the cheapest water-quality insurance there is. Choose sturdy lidded tubs, one per fish for larger animals, filled generously with tank water and a deep air space left above it. Goldfish need that oxygen reservoir; a tub filled to the brim and sealed is a trap. Line the car with plastic sheeting and towels, wedge the tubs so they cannot slide or tip, and keep them shaded, since a tub in direct sun heats with dangerous speed.
Have serious filtration waiting at the new home
Set the destination tank or pond up before moving day, filled, conditioned and running, and transport the old filter media wet in tank water to install on arrival. Goldfish water turns on filtration more than any other common fish's does: their waste load can overwhelm a fresh, uncycled filter in days, which is why the mature media matters so much. Match the new water's temperature to the old as closely as you can; goldfish tolerate cool water well, but a sudden swing of many degrees still shocks them, and warmth arriving too fast is as unkind as cold.
Settle them and then test, test, test
Acclimate each tub gradually with new water, release the fish, and leave them unfed until the next day with lights low. Then, for the first week, test the water daily without exception, because the pattern of a goldfish move going wrong is a slow ammonia climb that the fish tolerate silently until they suddenly do not. Partial water changes with conditioned water are your correction tool, made early and without drama. Watch the fish themselves for gasping at the surface, red streaking on fins, or a fish sitting clamped on the bottom; if you see those signs, test immediately, change water generously, and contact an aquatic veterinarian if the signs persist after the water reads clean, since a stressed goldfish can pick up infections that clean water alone will not settle.
A KinsLe Family Sharing plan for the move, who lifts which tub, who drives, who tests the water on which of the first seven days, puts the real work of a goldfish move on paper where the whole household can carry it, instead of leaving it to one exhausted person at the far end.