I usually use a cooler. For very long trips I'll add a battery-powered airstone. Freshwater fish are usually fairly hearty (especially the pleco). If you don't get to set up the tank right away - just keep an airstone in the cooler once you get there. Air is THE most important thing. I've had success with this for weeks (yes weeks... don't ask) for both fresh and saltwater fish (damsels). Also - give the fish something to hind in during the trip, like plastic/real plants or other items that will not crash and squish them.