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Silicone in the Aquarium Hobby
by Frank Mueller (fmueller)

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The details on silicone provided below are for informational purposes only. Neither Cichlid-Forum nor the author are responsible for anything that may go wrong with your tank or its inhabitants.

Silicone-sealed glass tanks have been the popular choice of aquarists for tanks up to about 240G since they replaced metal framed aquariums in the 1960s. Due to the higher cost, acrylic can only compete seriously for larger tanks or custom shapes. Given this popularity of silicone in the construction of aquariums, one might assume that it would be common knowledge what type of silicone to use for aquarium purposes. Yet surprisingly, people looking to buy silicone for aquarium projects - be it the resealing of a leaking tank or the installation of a DIY background - find themselves confronted with so much information and misinformation on the subject on the Internet, that it is almost impossible to separate one from the other. We have reviewed this information for members of, and find there are simple take-home messages:

  1. All pure silicone is aquarium safe once cured.
  2. Silicone with antibacterial and fungicidal additives might put fish at risk.

So far so good, but as so often, the devil is in the detail, which we will discuss in the remainder of this article.

Product Font Rectangle Bottle Liquid

Photos from manufacturer's websites. Added by Cichlid-Forum for illustration purposes.

Aquarium Safe - pros and cons of buying silicone with this label.

For those looking for absolute peace of mind buying an aquarium sealant that is labeled as 'Aquarium Safe' by the manufacturer might seem like a no-brainer. At the time of writing this article (Jan 2013) dedicated aquarium sealants are available in the USA under at least four brand names:

  • ASI Aquarium Silicone Sealant
  • All Glass Aquarium AAG65010 Silicone Sealant
  • DAP Household/Aquarium Adhesive Sealant
  • Marineland

In addition, aquarium sealant is available from companies like Glasscages. The main drawback of restricting your options to silicone with the 'Aquarium Safe' label is that this type of silicone is not always easy to find locally, and it tends to costs more than the equivalent product, which can be found at your local hardware store.

What brand should I use?

There are many brand names under which silicone is sold in the USA. As long as you make sure that what you buy is pure silicone, and you let it cure completely before exposing your fish to it, they will be fine. Since GE Silicone is probably the brand aquarists will most often encounter when shopping in big chain stores such as Lowes, Home Depot or Walmart, below we will discuss different types of GE Silicone in some more detail.

Not for Aquarium Use - what does this label mean?

GE Silicone I for Door and Window is a type of GE silicone that has been used by hundreds if not thousands of aquarists with excellent success. Many years ago, this product even used to carry the label 'Aquarium Safe', but it was dropped, and in some cases replaced by a label 'Not for Aquarium Use'. This has caused significant confusion and concern among aquarists. Since the ingredients of GE Silicone I for Door and Window never changed, and many people continue using it to this day, there is no rational reason to believe this product has lost any of its suitability for aquarium purposes.

Liquid White Fluid Personal care Bottle

Photos from manufacturer's website. Added by Cichlid-Forum for illustration purposes.

GE Silicone I vs. GE Silicone II - what's the difference?

Silicone I gives off acetic acid while curing, which causes a strong vinegar smell. Make sure to follow all warnings on the packaging when working with silicone. Avoid contact with your eyes or inhaling the funes. Make sure you work in a well ventilated area. The strong acidic odor, especially for people working with silicone all day, prompted the development of Silicone II. It gives off ammonia instead. It either is less damaging for people, or it smells so disgusting that folks are forced to wear breathing masks or take other precautions. Silicone II has about 20% less strength than Silicone I, but this is still plenty strong enough for building a tank. In many areas, Silicone II seems to be more readily available in colors like black and brown.

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