I built a sump out of acrylic. I used Weldon #4 to weld the pieces together. Since your tank already has the pieces that should fit together perfectly, you just apply a thin bead of the weldon (#16 would work fine too but #4 makes a stronger bond), apply pressure (books stacked on top would work) and let it sit for 48 hours. The longer you let it sit like that, the stronger the weld will be.
I wish I could stumble across a deal like that, I live in Kansas and there are no tanks like that out in the Midwest. Great find, Take your time and get it restored to new.
i forgot to mention that i may have gotten this thing for free! and it goes like this. my grandma gave me some dressers- i traded the dressers for some r/c cars- then i talked this guy into trading me the tank for the r/c cars= no $ invested(as of now i still need to fix)