Hi, I'm trying to finish the designing stages before I build my custom concrete tank. I plan on the inside dimensions being 8ft long x 3ft wide (may possibly go 5ft wide) and 5.5ft tall. I will have two viewing windows in the front that will be 4ft by 3ft and have a one foot concrete pillar seperating them. The windows will be set into a lip from the inside of the tank with 3 inch angle iron as extra support. The biggest concern obviously will be the glass thickness. I plan on going 3 in thick acrylic for extra safety. Also I've read that having a "closed top" or "framed top" will help support the tank and minimize bowing. I was wondering if i pour a 6"x6" or a 4"x4" pillar connecting the front to the back on both sides and in the center where the pillar seperating the windows will be will be adequate enough to help support the tank enough. this will be my first build of a custom tank, although I will have help from friends with several years experience working with concrete. I want to make sure I cover ever angle and have all the bugs worked out before I build the tank and have a disaster happen. Also after the tank is poured is it best to let the concrete cure then place the glass in or should the glass be placed in once the concrete has dried enough to support the weight of it and then filled with water to finish curing. Will take any advice I can get. Thanks