Would it make any difference to a trio of guppies if they were put together to mate in a 5 gal plastic tupperware versus a 5 gal glass tank? Would they be too scared.
Target has some 8 gallon bins that I've taken on trips to keep fish in the room in (i put abot 5 gallons in them). What matters is heat and filter and that is for keeping them alive, not for mating.