I have just recently got back my tank. It was being resealed as a leak had formed two days after filling it up the first time.

I place a 1/2 inch pink insulation (the kind used for the exterior of the house)under the tank. The tank sits snuggly on the insulation however on the backside there is a 2-3 foot section where there is a 1/16 gab. I can pull the insulation up and down in that area. Should i be concerned? I will be putting 175 lbs of live rock, 75-100 lbs of sand, and with the weight of the water will that close that gap?