I personally think that regular 2x10 would be sufficent if designed properly and there is no need for lvl.
Yes it is stronger but if a stand is built properly and distributes the load of the tank evenly you will be fine doing it without the extra cost
My problem is that since there will be a tank
Underneath it that I will have no center brace on a 8 foot by 4 for wide tank. Can lvl support the weight of a 600 gallon tank suspended 60 inches into the air with support on just the 4 corners?
Lvl's are incredibly strong. I can't imagine them breaking under the weight of the tank you want to put on them. Just as important is how you plan to build the legs and make certain it's solid so that it can't twist or collapse when someone bumps into it all.