built 2 racks out of pine plywood never sanded or sealed it. since the snake tubs and rack were set up wit hthe lids installed. ( this way I can pull out thetub and set down if I have to replace the flexwatt with worrying about a runner escaping.) I used 3/4 for the sides and back andshould usethe same for the shelves. I did use pieces of 1x2 to attach the shleves to the side ( shelves are screwed to the rail( 1x2) which is screwed to the side plywood).

Here a picture of the finish rack. ( had to cut and place supports to the front and back( not seen) cause I used the thinner 1/4 thick plywood for the shelves.