Aquariums are made of two types of materials… glass or acrylic. This article discusses the following 12 criteria and compares the two materials accordingly:
• Impact Resistance
• Long Term
• Tensile Strength
Glass has been the aquarium industry standard for a long time, and is available everywhere. The popularity of acrylic, on the other hand, is relatively new. Acrylic aquariums may not be available in all pet stores. A special order may be required which will increase wait time and cost. They are, of course, available online but buying an aquarium, sight unseen, can be risky. Returning an item of this nature that is not right or is damaged in transit increases wait time and cost.
Compared to acrylic, glass is much less expensive per gallon. Acrylic aquariums are likely to be 2 to 3 times more expensive than glass, even though acrylic is cheaper to manufacture and due to its lighter weight, cheaper to transport. This has to do with the fact that glass aquariums are more popular and thus more of them are manufactured. However, because acrylic weighs so much less than glass, larger acrylic aquariums, typically 150 gallons or more, can be found to be much less expensive than their glass counterparts.
Clarity (Light Transmission)
Thinner walled aquariums will show little difference in terms of clarity between acrylic and glass, so it is more cost effective to get a glass aquarium if buying only 10 or 20 gallons. Any thicker and the more obvious the clarity of acrylic will be. Acrylic allows for 92 to 93% light transmission at 5mm thickness, whereas in comparison, glass allows for 88% light transmission at the same thickness.
The reason is regular glass, the thicker it is, the more of a green tint will be evident. This green tint is due to the iron content of the sand used to make the glass, and this creates the inferior clarity in glass compared to acrylic.
This green color is most visible at the glass panel ends. Sometimes people look through their aquariums lengthwise and notice a slight green tint to the water and commonly assume there is an algae problem. This might be true, but if the aquarium is made of regular glass, then the water will falsely appear to have a slight green tint to it. The green color can be remedied with high color temperature LEDs, lights with some blue LEDs, 10K or higher lighting, or cool temperature LEDs.
High-grade low-iron glass (aka Starphire glass) is manufactured from silicon with a low iron content. It has about 5-6% more clarity than regular glass, has up to 91.5% transmission at 5mm thickness, and is almost as clear as acrylic. However, this type of glass is much more expensive.
Mid-grade low-iron glass has a blue hue, and can be more or less transparent than regular glass, depending on manufacturer.
Low to mid-grade low iron glass can have worse clarity than regular glass depending on manufacturer; it can have a blue tint which can be darker than regular glass.
Distortion (Light Refraction)
When you look into your aquarium at an angle, the colors and locations of fish will appear to be slightly off. This is due to light being refracted as it passes through the aquarium walls. Acrylic aquariums show the truest color, size and location of everything in them due to acrylic having the least distortion (light refraction).
Glass will chip easier, whereas acrylic will scratch easier. When it comes to glass and scratching, there is less concern when scraping algae or when disturbing the substrate with a gravel vacuum. The fact that acrylic scratches so easily can make cleaning a major chore, and this reason alone, despite all the advantages of acrylic, might be enough to choose glass.
Glass is harder and won’t scratch as easily as acrylic. Scratches on glass are permanent; whereas scratches on acrylic can be buffed out but can be challenging. When scraping glass with a razor blade, use only new razor blades, and carefully, only if necessary. Better to always use a product specifically designed for the task. Never use a razor blade on an acrylic aquarium!
Glass has high scratch resistance, and razor blades can be used to scrape the surface clean. Acrylic has low scratch resistance, never use razor blades to scrape the surface clean, use only a product specifically designed for the task of scrapping algae from acrylic aquariums.
WARNING: There are videos on the internet that show people using original non-scented Mr. Clean Magic Eraser pads to clean their acrylic tanks without scratching. The “magic” in the Magic Eraser is melamine foam. The foam wears away much like a pencil eraser, leaving behind a residue. DO NOT use this product and be wary of internet advice!
Keep in mind that unsupervised children might touch an acrylic tank with anything other than their fingers, and pets such as cats may paw or claw at the sides. Be careful when aquascaping inside an acrylic aquarium; place gravel, rocks and driftwood carefully and gently avoiding contact with the panels.
The plecostomus species of fish are well-known algae eaters native to rivers of the Amazon region of South America. Plecos feed via a specialized mouth that allow them to attach themselves to hard surfaces. In the wild, they scrape the algae from rocks and wood. In your aquarium, they will do the same to your glass or acrylic. Glass is a better option if you are going to include any plecos, especially the larger ones, as they will scratch acrylic aquariums while feeding.
Based on popular opinion it is possible that plecos can and will cause damage to the silicon holding the glass panels of a glass aquarium together. If this is happening, it is likely that either the pleco is not getting enough food or there is no driftwood for it to chew on. Always include driftwood in an aquarium holding any plecos.
Acrylic has 7 times more impact resistance than glass. This might be an important consideration if the aquarium is to be kept in an area where there might be accidental impacts with the sides, such as where there are unattended children.
Insulation (Thermal Resistance)
The insulation, aka thermal resistance, of a material is how much resistance it has to heat transmission from one side of the material to the other. The insulative quality of an aquarium might be something to consider if it is kept in a cool place or if there are wide temperature variations. Heat travels 10-20% faster through glass than it does through acrylic. So, if energy efficiency is preferred acrylic would be the better choice.
Glass aquariums are manufactured as 4 separate panels glued together with silicone. The silicon seams may need to be replaced about every 10 to 15 years but have been known to last longer. In comparison, acrylic aquariums have no seams because their panels are welded together. There are glass aquariums that have no silicon. These are rimless glass aquariums, and their edges are fused together with heat. These aquariums are very expensive.
Some types of acrylic, such as extruded, can yellow over time, whereas cell-cast acrylic doesn’t turn yellow. Also, cell-cast is 4x stronger than extruded acrylic. If in doubt as to whether the acrylic in an aquarium will turn yellow over time, ask if the aquarium is made with cell-cast acrylic. The acrylic panels from most reputable manufacturers will be made of this newest material.
Tensile strength is how much pressure a material can take before losing its shape. Glass has 2.5 times more tensile strength than acrylic.
Acrylic can be shaped and molded into virtually any configuration. Glass is much less forgiving to configure shapes and bends, so while there are bow-front glass aquariums, custom shaped glass aquariums are much less common than acrylic ones. Acrylic is much more versatile when special order designs are involved and may be much more expensive.
Acrylic can be augmented easily. Drilling holes for bulkhead fittings, for example, is easy and can be done on acrylic with simple tools. Trying to do the same on glass requires expensive tools and a level of experience that without runs a high risk of breakage.
Repairing a crack on a glass tank usually requires replacing the entire panel and resealing with silicon, which can done rather cheaply, especially on smaller tanks, but is not easy. Because glass tanks are the industry standard, finding a used same size smaller “parts” tank at a fish or thrift store might be easy. But if a piece of glass needs to be cut to size, other than cutting thin glass (4mm), most other glass work must be done with professional diamond coated tools.
Acrylic doesn’t easily crack, but if it does, it can be repaired without the need to replace entire panels. While acrylic scratches easily, those scratches can be easily buffed out, whereas scratches on glass are rare but permanent.
Glass weighs 2.6 grams per cubic centimeter, whereas acrylic weighs 1.2 grams per cubic centimeter. This might be of concern if a large aquarium must be shipped long distances. Cost is a factor. Also, if there is ever a need to move the aquarium around, weight will be a huge factor if the aquarium is glass, and may require more than one person.
Glass aquariums need to be supported only along their edges, whereas acrylic aquariums need to be supported along the entirety of their bases.
When choosing the right aquarium, there is more to consider than material of manufacture. A previous article discusses considerations based on aquarium size and shape; Choosing the Right Aquarium Size and Shape.
About author and webmaster… Troy Boylan
Ecoculture Village Founder & President, Anthropology BA, Interdisciplinary Studies: Ethnobotany BS. Two things I think are worth anything at all… all things wilderness and ecoculture… and well, RPGs… and skateboarding!
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