240 Gallon Setup time

Hi all,
Stepping up to the 240 gallon level. Tank is in, plumbing installed to a 90 gallon sump, Holey Rocks from craigslist in, filled with water. Problem is, the 90 used to house a turtle, and I don't know the history of the 240. Not sure, but I think I would like to put a gallon of bleach in and run it for an hour or so, then drain it and refill it before I begin adding the filter material, and substrate. Any thoughts?
Thanks
Dan

Strange. I replied to this right after you posted and it didn't show yet. I will try again. I see no silicone issues with the 90, and it is holding water just fine. I have added the bleach and letting it cycle in the tank for a bit then replacing all the water and beginning my cycling process. Can't wait to move the inhabitants of my 90gallon over to it. (but I will... )

Lol, It was out in the garage drying. It is in place now. I have 250 pounds of Ivory Coast gravel on order, and looking for 200 more pounds of holey rock. The water cycling has begun..