If you are just getting a tub that isn't going in a rack I would get this exact tub (Sterlite 41 qt underbed box) Dimensions: 34-3/4" L. x 16-1/2" W. x 6" H.
http://www.doitbest.com/Storage+tote...sku-624136.dib
As far as racks go I would stick with the IRIS line racks that AP makes. You are going to need to get a rack for hatchlings/Juveniles and a separate rack for adults.
The 375 series for hatchlings/Juveniles
The CB-70 Series for adults.