Biknut, I think that a block of aluminum that size would be around $12. I got mine for free, I told my Dad what I intended to do and some blocks of aluminum "disappeared" from where he works.
Also, I will get the camera out shortly for that close up pic.
Goat Herder, Yes I made the tank. Like I said before, I am no welder. Actually the tank is brazed together, but the problem is that it leaks despite the fact that I used Kreme on it. I wanted to do a fiberglass tank, but everyone around me said OMG YOU SHOULDN'T DO THAT BECAUSE I DON'T KNOW ANYTHING ABOUT IT AND IT DOESN'T MATTER IF YOU DO BECAUSE I DON'T!!!!! so I made a metal one... and it leaks. LOL, so I'm doing it my way next time.