That table is definitely a non-starter for this project. Between the multiple dead fish and all the other nonsense that's been going on, I suspect you may be skating on thin ice with your parents. If/when that table implodes, you will have an EPIC disaster on your hands.
Is this the tank that is leaking? If so, you need to empty it anyway. Take advantage of that by making a stand out of a few concrete blocks and a sheet of plywood. That is easy, cheap and super-strong. Sorry, but that table is a joke. How did you test it? Did you apply 500 pounds of pressure downwards on it? That's the minimum it needs to withstand, on a continuous basis.
Don't take this the wrong way, but you have demonstrated a propensity for not listening to other people's advice. For your own sake, please listen to what we are telling you now.