Building an aquarium that will provide the best environment for your chosen fish requires choosing the proper glass thickness. Getting glass that is too thick will cost additional money, but getting glass not thick enough could cause a leak in your tank. Many people underestimate the weight of the water required to fill an aquarium. The average 4-foot aquarium weighs 150 to 175 pounds. Thus, it is important to ensure your glass is strong enough to support that weight.
Consider the glass safety factor. Limitations of the glass manufacturing process lead to wide variability in glass strength. Look for a glass suitable safety factor of 3.8. The glass suitable safety factor is an equation that calculates the safety of the glass when taking in to account its height, width and thickness. A lower number than 3.8 indicates lower quality, which is more likely, though not guaranteed, to break.
Consider what type of fish will be living in your tank. Small fish like mollies and guppies are fine in a 2-by-1-by-1-foot tank. Larger fish and smaller cichlids need a deeper tank sized 3 by 1.5 by 3 feet. Larger cichlids like oscars are better off in a 4-by-2-by-2-feet tank.
Decide on the size of your tank. Five-millimeter glass will suffice for a 2-by-1-by-1-foot tank, but any larger requires at least 6 mm. Two-by-1.5-by-1.5-foot or 3-by-1.5-by-1.5-foot tanks require 8mm glass. Two-by-2-by-2 or 4-by-1.5-by-1.5 aquariums require 10mm thickness. Any larger requires 12mm glass thickness.