it will weigh more than 700 ;-) i have a 55 gal on a wooden floor. but what you need to find out, is what way the beams go and what thickness they are, i have my tank running parralel with the beams which are 7 x 2" timbers and that holds fine. In my case i had to have the tank paralel on the beams, but try to get yours to cross over the beams thus spreading the weight, and also dont have it away from the wall, keep it as close to the wall as possible thats the beams strongest place. Also make sure your tank base is solid and not on legs of any sort. To work out the weight of your set up, i must admit i did it the long way, but well id adds up correctly,
4.5 litres to 1 gallon
1 litre of water = 1kg
2.2lbs into 1kg
so........ heh
65 gallons = roughly 643.50 lbs (thats only the water) but also that calculation is for "normal" water, salt water is heavier by about another 30lbs roughly
basically the whole setup will be knocking on for half a ton
hope this helps
sorry for the long post but i think its quite important to know how much these things actually weight, especially if your putting one on wooden floors