Packed in rounded corner plastic bags, 1/4 water and 3/4 oxygen carried in polystyrene box with lid. Few fish per bag. If cichlids, or stroppy fish, one fish per bag. Make sure bags are tight fitting in the box and not able to move around. Newspaper scrunched up is good and added insulation. If you are worried about temperature (unlikely to be a problem, except for overheating, this time of year) fill a plastic fizz bottle with hot water and wrap it in a towel to pack in the box with the bags.