This porduct is designed to help your copperband get to the food before your other greedy fish! The screw top allows you to place your frozen food cube inside and tightly fasten it. The magnet will work for glass up to 20 mm.
 
The package allows you to either use the tray and put 4 cubes of frozen food in place or you can take the tray out and place larger blocks in place! Included also are 2 different lids with different sized holes to allow for larger copperbands.