I don't understand the sketch. Are you planning an 8 foot long, 2 foot depth, 2 foot high tank? That would use a 2 piece front (unlikely to work), a plywood back, one front cut in half for the two ends, and what for the bottom?
Ha, I did the sketch up and typed this in a hurry during my lunch break, thanks for asking for the clarification. Normally I would have separated the three in separate snapshots, and I will update them as soon as I get a chance.
There are three different tanks in the sketch:
the top one has the plywood back and uses 4 side panels on the sides, 2 front panels for the front, and I was thinking the two bottom pieces with the two back pieces, but thinking it through... that won't work because the back is taller than the sides are deep, it would have ended up 2 feet deep and 2 feet tall by 8 feet long.
The second one (bottom left in the first picture we'll call it "plan A" ) is basically taking one panel (front/back) off each tank and joining them where the removed panels were. It would make it 2' deep by 4' long by 2' tall
The third (bottom right in the first picture, "plan B" ) takes one of the side panels off each tank and joins them where the panels were removed. this would make it 12" deep by 8' long by 2' tall.
As soon as I get back on my laptop, I will fix the below pictures, i'm sorry for the confusion.