About Platinox panel for tank....I believe primary purpose is for sound deadens material with stainless steel finish. If you still want metal tank, you need 316 SS which is more nickel, tougher (less prone to crack) and food grade to avoid any rust. Otherwise go for roll cast plastic tank.
For choosing SS of your choice:
For welding 304 SS, use 309 SS wire at .032 to .035 dia. Mig.http://www.azom.com/details.asp?ArticleID=965
For welding 316 SS, use 316L SS wire at same above dia. Mighttp://www.azom.com/details.asp?ArticleID=863
Sojourn for Christ, Jerry