The short answer for a fish that fears heat, not cold
A white cloud mountain minnow travels best in a doubled bag of its own tank water inside an insulated box that keeps the water cool and steady. Most tropical packing advice is about preventing chilling, and this species turns that advice around. White clouds come from cool mountain streams and live happily at temperatures that would worry a guppy keeper, while a hot car or a sunny windowsill can push a small bag into dangerous warmth surprisingly fast. So the long journey plan for this schooling fish is simple: bag the group together, insulate against heat, and travel in the coolest part of the day you can manage.
Preparing the school for departure
Fasting the minnow school for a day before the journey keeps their travel water clean, and it is the only real preparation this unfussy species needs. Catch the fish calmly with a wide soft net or a submerged cup, working in the morning when they are settled rather than darting at feeding time. Keep the whole school in one generous bag or split it across two, because white clouds are committed schooling fish and a pair travelling alone behaves nothing like a confident group. Check as you catch that every fish is active with fins spread, and leave behind any individual that is already hiding and listless at home.
Insulating against warmth instead of cold
Tank water from the minnows' own aquarium fills the inner bag about one-third full, with plenty of air tied in above it before the bag is doubled. Stand the bags in the insulated box and cushion them upright, then think about where that box rides. A shaded footwell serves white clouds far better than a seat in the sun, and a box pressed against a heater vent can overheat even in winter. In genuinely hot weather a cool pack wrapped in cloth and placed outside the bags, inside the box lid, blunts the peak without chilling the water directly. Never add ice to the bag itself, because a local cold shock is as unwelcome as heat.
Travelling through a long day
Keeping the box closed and shaded is the whole in-transit routine for white cloud mountain minnows. Their tolerance of cool conditions means a long journey, even an overnight pause in a cool room, worries them far less than it would most tropical fish, provided the box never sits somewhere hot. Feed nothing on the road, carry the box indoors during long stops, and avoid the classic mistake of leaving it in a parked car while you eat, since cabin temperatures climb fastest exactly then. If you must check anything at a stop, feel the outside of the box rather than opening bags and warming them with light and handling.
Settling minnows into the new tank
Floating the sealed bag in the destination tank still matters for white clouds, because even a cool-tolerant fish deserves a gradual meeting between bag water and tank water. Open the bag once temperatures feel close, add tank water gradually, and release the school into dim light with plants or cover available. They typically colour up and start exploring quickly once settled. Offer a small feed later that day and watch for fish that stay apart from the school, breathe heavily, or lose their red fin edges to a washed-out grey, seeking an aquatic specialist's advice if the group does not settle. Writing the school's preferred temperature and foods into a KinsLe Pet Passport stops a well-meaning receiver from housing these minnows in water kept warm for tropical tankmates.