 Special measures to reduce losses through this behaviour are therefore required if the aquarist is interested in obtaining as large a yield of fry as possible.Special 'egg traps' have been devised for the purpose - these may consist of evenly spaced glass rods in a frame, a layer of glass marbles on the aquarium bottom, or some other such device.The purpose of all these designs is the same - to allow eggs to fall through small gaps into a space where they will be beyond the reach of the adults, who are unable to pass through the same gaps.