Glass, Starphire glass, and acrylic tanks.

Starphire glass and acrylic are both very clear; however, there is a certain amount of distortion when looking through acrylic at an angle that is not apparent when viewing through Starphire glass at an angle. Acrylic is much lighter than glass. Acrylic is a better insulator than glass, which can be either a positive or a negative depending on your particular environment. In a cold climate, acrylic will retain heat better than glass. Unfortunately it will do the same in a hot environment, too. Acrylic is much less likely to spring a leak than glass.

Starphire on the right in the picture below.

On the other hand, acrylic is much more likely to fail due to overheating from the lighting fixture than glass. One must always exercise caution in the placement of metal halide lamps over the top of an acrylic tank. More clearance is required for an acrylic tank than for a glass tank. In spite of all of it's obvious advantages over glass, acrylic has one fatal flaw that most people just can't accept: It scratches! Easily! Just about anything will scratch acrylic. Over time, it will become dull from the abrasive action of cleaning coralline algae from it's walls. Even some fish will leave marks on the surface of acrylic. That doesn't happen with glass. Acrylic tanks are more expensive than glass tanks in the smaller sizes but larger Starphire glass tanks are more expensive than acrylic tanks of the same size. You reach a point where Starphire glass just becomes prohibitive due to cost and weight factors.

That hasn't stopped some folks from buying large, custom Starphire tanks in the 700+ gallons size range. Wayne Shang has a gorgeous 718-gal Starphire tank that was built for him by LeeMar in California. It was made with 3/4" Starphire (when they still made it) and it measures 96"L x 48"W x 36"H. It has a 4" Starphire glass perimeter euro brace and a single narrow Starphire glass cross brace in the middle. I'm sure it was quite expensive. He lives in Fremont, California on the east side of San Francisco Bay. He is definitely in an earthquake zone. He prefers glass over acrylic. In general, acrylic tanks are popular in the SF Bay Area than glass tanks. In the 1989 Loma Prieta quake, glass tanks were more likely to fail than acrylic tanks. There is a thread on Reef Central of an 800+ gallon tank that has a 3/4" Starphire front panel that is 10' long. That tank measures 120"L x 45"W x 33"H (if I remember correctly). It was custom built on site about 10 years ago.