a big net and a big bag if not moving far
if your moving any large distance you could sedate it ask at your LFS about it you just add teh chemical to the water and it dopes the fish up quite safe and lasts a certain amout or hours saves it getting over excited and hurting itself
if you are going far it may be best not only to sedate the fish but also pack it in polistyrene and to fill the bag with oxogen i have done this before when moving koi carp over a long distance they were around 3-4 foot in size but the same rules kinda appley to tropical fish also.
hope was of some help