prolly about 75-90 gallons.
question: im new around here, what the heck are these dragonfly/mosquito lookin flies around here? never seen them on the coast b4, and now there everywhere i look..... literally!
I guess I should have asked which way the L was going to be pointed, are you looking for a drop off like a cliff or just a L shape on its side. Either way if we went with a 36"L x 24"w x 18" with a drop of 36" you would be right at 100 gallons. If we made it 30" x 24" x 18 with a drop of 30" we would be right around 70 gallons. I would say the thinnest acrylic used would be 1/2 " thick and we would need about two full sheets.