5" or even larger RES will be needed or most will become expensive bass food. Sourcing larger RES can be a challenge as they are difficult to pellet train so few hatcheries grow them out. You may want to try to catch some larger adult RES from a local lake and transfer them. Keep in mind the legal issues possibly presented with this along with the possible transfer of disease and other unwanted hitch hikers. The next month is generally best for catching adult RES off their nests...