Originally Posted by JOMA
this will help the structural integridy?
That won't help with structural integrity, but will spread the load. You need something like a 3/4" or thicker plywood ... make sure it is bigger than the entire top of the shelf. Then when you place the tank on it, it will spread the load to the sides of the bookshelf, preventing bowing of the shelf itself.
For such a small tank, I don't think it is absolutely necessary, as long as it is sturdily built ... no wobbling, etc ... The tank is only 40 lb. I would just put 40 or 50 lb weight on the bookshelf & see how it behaves. <I wouldn't use the tank with water .... too much mess if it starts tilting & spilling water all over!>
For bigger tanks, I would reinforce the shelf by gluing & screwing a couple 2x4's on edge below the shelf to stiffen it. You can make the stand even more rigid by fixing those 2x4 beams to the sides with screws or brackets.
I think your bigger risk is water in the particle board. If you get that stand too wet, it will swell the particle boards & weaken it severely, causing a collapse ....