I am a contractor and have seen/repaired many problem floors. My advice is not to put anything between your floor and stand. All you are asking for is discolored flooring or mold. Almost any protective covering will become welded to the floor over time and it will end up looking worse than having nothing at all if you decide to move things. Seen it happen so many times under heavy furniture, etc. Best thing is to contain the water INSIDE your stand. Any water spills outside your tank...just mop it up with a towel. Also, if possible, provide something in your design to allow airflow under your stand even the smallest amount will greatly preserve things.
Thanks for the advice. Do you think if I put down that liner everyone is talking about inside the stand, under the board where the sump will sit, and drill holes in the back of the stand along the bottom 2x4 that would help at all? I'm putting the tank in front of a base board heating unit. Would there be anything bad about that that I may not be thinking of?