To sort fish into a variety of sizes, multiple panel bar graders of various spacings work well. Grading boxes are used to sort large numbers of minnows or fingerling fish. These boxes vary in size from small units for use in tanks to larger ones designed to handle more fish in ponds. The boxes usually float. Both pond and tank grader boxes can be constructed with frames that accommodate standard sized grader panels with various bar spacings.
Some commercial boxes have simple adjustable or interchangeable bar graders.
A series of grading baskets with various bar spacings can be used to sort mixed sizes of fish. The grading boxes can be enclosed on the sides and bottom with galvanized hardware cloth, but plastic coated wire cloth is preferred because of greater durability and less injury to fish. Sorting or grading tables work well when hardy species require accurate processing for research or breeding purposes. Tables can be portable or food-sized fish. They usually have an 18-inch wide skirt inside the net with floats to prevent fish from jumping out of the enclosure.