The quality of a glass aquarium is very important – it’s where all the seawater will be contained and where all the livestock will live. When an aquarium is full of seawater there is considerable side pressure from inside and in addition the base needs to be able to take the weight of seawater, sand and rocks. If the aquarium failed once all stocking had been completed it would be a serious problem.
The strength of the aquarium is decided by the glass thickness, the bracing and the quality of workmanship. The larger the aquarium is the thicker the glass needed. Very small aquariums are often safely made without bracing, but as they get larger bracing is required.
Nowadays commercially built aquaria are usually built to laid down standards but a check is still worthwhile before a purchase is made. If the aquarium is to be home built, and this is accomplished fairly regularly, then the correct glass thickness needs to be ordered. The glass used is normally float glass.
When checking an aquarium before purchase the construction quality can be judged. First, look at the glass panels. There shouldn’t be any blemishes in or on the glass. If edges can be seen, such as at the top and the corners, the sharpness should have been neatly removed and a smooth slightly rounded edge left without overlarge chips. The longest sides of the aquarium, that is the front and the back, should overlap the end panels not vice versa.
Second, silicone is used for glass aquarium construction and it is very strong and reliable. The silicone should have been applied well so this is checkable. Though a waver in the silicone line is not necessarily detrimental, serious ones could be as the width and thickness of the bead could be reduced. So the silicone lines should be reasonably straight. Also, there shouldn’t be evidence of trapped air within the silicone bead, a tiny bubble here and there may well be acceptable but many bubbles are not.
Aquarium glass should be braced against the internal pressure exerted by the seawater. As said, with very small aquariums this is often omitted. As the aquarium increases in size, including vertically, it is usual to use bracing struts at the top to increase strength. Aquariums of 2 x 1 x 1ft (length x breadth x height) sometimes have bracing, sometimes not. If the height is over 1ft then bracing is recommended. The bracing is usually constructed of the same thickness glass used for the panels of the aquarium. The best method is to have a brace running down the length of the longest glass panels, with the edge siliconed to the panels. Attached to these are the cross braces (front to back) which are usually siliconed underneath the front and back ones. The number of braces used depends on the aquarium length – smaller ones have two, one at each end, and larger ones three, the extra one in the middle. A 4ft aquarium would be expected to have at least three. Ones that are longer than this have more, the number subject to length.
If the glass used in manufacture is thicker than the guideline, no matter. If it is thinner, then pay attention to the bracing that has been used, as the manufacturer could have created strength by increasing this. However, glass that is thick enough overall and braced is best.
The guidelines for glass thickness:
(Measurements are Length x Breadth x Height in feet. Glass thickness is given in millimeters)
2 x 1 x 1 5mm
2 x 1 x 1.5 6mm
2 x 1.5 x 1.5 8mm
2.5 x 2 x 2 10mm
3 x 1 x 1 6mm
3 x 1.5 x 1.5 8mm
3 x 2 x 2 12mm
4 x 1.5 x 1.5 10mm
4 x 2 x 2 12mm
6 x any length x 2 maximum 12mm