Worst case scenario - tank leaking!

[Electric Warrior]

I just got the last of the water out of the bottom, and 99.9% of the sand out, and it definitely looks like the previous owner resealed it himself, because it's not a pretty job... The seals up the tank look very clean and no evidence of turning white or any bubbles or anything, but I take it that I need to just do the whole thing, rather tha just the bottom?