Here is a hatchling rack that Tim Bailey(muddoc) made for me a few months back.He has the plans to make it on his web site in detail.He used 2 peices of 11" heat tape on the back for heat source.I am able to use 4 12qt tubs on each shelf x 9 with a total of 36 tubs.I did find another use for this same rack i can place 1 41qt tub on each shelf along with 2 12qt hatchling tubs .Here is a pic of the unit.