To protect a floor from leaking water, you can use the rubber shower liner from HD. They sell it from rolls, you pay per foot. Build a wood frame a couple inches bigger than the bottom of your stand and attach the liner to it. You can paint the wood and liner that's exposed so that it doesn't stand out so much. You can calculate the size of the liner and height of the frame to get a rough idea of capacity to hold water, but subtract some for the volume of your stand within that area. Hopefully leaks or splashes out of the tank will be small, and a water alarm placed inside the frame will scream at you when you forget to close a valve.