Originally Posted by Mumma.of.two
The sand won't effect it because of gravity.
You said the waters about 1/4 of in inch lower in one corner (not both front corners?) so that's a cause of concern to me. From what I've read tanks take most of the weight of the water on the corners then the outside edges. The middle of the bottom glass doesn't need supporting. If its only a few mm gap and it doesn't extend further than a few inches it might not be a problem though.
Just googled it and according to what I've read, as long as the BASE of the tank is level and not uneven in anyway, there is no worries. Read stories of people with 90+ gallon tanks that were up to an inch uneven and they had no issues. So, I'm not going to sweat 1/4 inch unless I start to see some leaking
I dont even think mine is a whole 1/4 off after looking at it again.
EDIT: Just measured from the botom trim to the top trim on both sides and it appears that the side that has the lower water line has the trim peice up higher. When I ran my hand around the inside of the trim I noticed that it had been siliconed back in place. I think just the trim is uneven,