The aquarist when listing the equipment required for a marine system obviously runs into the aquarium questions. These are, first, what size is it going to be, then what shape is it going to be? There may be similar considerations for a sump if one is going to be used.
At the point of purchase sometimes another question – or rather choice – arises, glass or acrylic? At this point more often than not the choice is made automatically, as few retailers stock aquariums in both glass and acrylic, particularly in the same size. So what are the advantages or otherwise if there is a choice?
Often a glass constructed aquarium is cheaper, particularly if the aquarium is made to measure. Glass can be cut and silicone glued quite easily to whatever the aquarist wants. If the purchase is to be a standard size, then glass again is often cheaper, but sometimes cost is the other way round for some reason, possibly because standard run manufacturing works out cheaper by the unit.
Glass aquariums, properly made with the correct thickness of glass for the aquarium size, and with silicone joints properly applied, are immensely strong. The silicone will not fail under the pressure, the only failure will be with incorrectly applied silicone. Incorrect application includes air bubbles in the silicone that can weaken it, and bad adhesion because of poorly prepared glass glue surfaces. The strength of the glass aquarium is also assisted by correctly placed and sized cross-struts. So obviously one requirement when purchasing a glass aquarium is to ensure it has been manufactured by a reputable company.
The acrylic aquarium is also immensely strong and will not fail under normal usage. A reputable manufacturer is again a requisite.
Acrylic will scratch more easily than glass, so in use the aquarist has to be more careful when cleaning and the like. Sand inadvertently rubbed up against the surface, or too vigorous rubbing to remove persistent algae can cause this scratching. Scratches can be removed by polishing, but often this entails lowering the water level, not always practical. Glass will also scratch, but it takes more effort to create the scratches. It is more difficult to remove scratches from glass.
It has been said that acrylic gives a much more transparent view into the aquarium. I have not been able to appreciate this, most aquariums that I have seen have algae, even small traces, on the viewing panels.
So the bottom line is: whatever! If the price is right, and the shape /size is as well, then the aquarist need only satisfy him/herself of the manufacturing source. Personally, my aquariums have always been glass, and I have had no room for complaint. Then again, how many complain about acrylic?