SILCONE BASICS:

Silicone rubber is a unique synthetic elastomer made from a cross-linked polymer which is reinforced with silica. Its characteristics are such that it provides a balance of mechanical and chemical properties useful for bonding glass aquariums (not acrylic).

The basic formula is: Me3SiO(SiMe2O)nSiMe3

RTV Silicones are the silicones commonly used for glass construction and is often sold in Home Improvement and Pet Stores (or online)

RTV Silicones consist of polydialkylsiloxane with terminal hydroxyl groups (groups made up of an oxygen atom and a hydrogen atom connected by a covalent bond), which are reacted with organosilicon (chemical compounds containing carbon silicon bonds) cross-linking agents. This operation is carried out in a moisture-free environment and results in the formation of a tetrafunctional structure (A chemical structure that possesses four highly reactive sites). Curing takes place when materials are exposed to moisture. Atmospheric moisture is sufficient to trigger the reaction, and thickness should be limited if only one side is exposed to the moisture source. Curing is also relatively slow, reliant on moisture ingress into the polymer which produces Acetic Acid vapors.

Different formulas and (combined with temperature and outside humidity) will affect cure time. Dow Corning and GE have proprietary formulas that cure at an even slow rate as compared to some cheaper formulas, especially used in construction where this is not an important factor.

100% RTV Silicone Rubber Sealant produces a flexible, durable weather resistant seal between similar and dissimilar materials; RTV Silicone provides excellent adhesion to tile, glass, porcelain, ceramic, fiberglass, non-oily woods, plaster, painted surfaces, metal, many plastics, and rubber. It will withstand temperature extremes from -60°F. to +450°F. and is waterproof for freshwater or saltwater use.

You will note that plastic (which is made from oil) is not mentioned. RTV silicone is not useful for bonding acrylic aquariums and the oils within acrylic will eventually cause peeling away (lack of adhesion).

AQUARIUM APPLICATIONS:

RTV Silicones are useful in the construction of glass aquariums and sealing the joints in DIY wooden aquariums. Silicone is NOT useful for acrylic aquariums as it will peel away over time due to the inherent oils in plastics.

Not all silicone formulas are the same, as stated earlier, Dow Corning and GE produce a RTV silicone that cures at an even and slow rate necessary for aquariums. Why is this important? Too fast a cure will not allow proper surface adhesion especially in important seams. It is also hard to work with in building aquariums and the person needs to work very quickly (usually too quickly) for proper aquarium construction.

Also you want to purchase pure 100% RTV Silicone as many (including ones produced by Dow Corning) have other ingredients for different applications such as fiberglass.

A good example of a silicone you do NOT want to purchase is Dow Corning Marine Sealant which I have actually seen recommended for aquariums! This product is great for fiberglass hulls of boats however it lacks the proper strength for aquariums due to added ingredients that allow for adhesion to plastic.

SUMMARY:

Can you easily purchase the proper silicone at a Home Improvement Store? The answer is yes, just do not purchase anything other than 100% Pure Silicone (color does not matter) and I strongly recommend brand loyalty has there are good reasons behind GE and Dow Corning patents. To be safe, if you are unsure of the silicone you are buying, don not try and save a few bucks at the local hardware store when your local Pet Store or Aquarium Store have the correct product for maybe a few dollars more (unless an exploding aquarium in the middle of the night is your idea of excitement)

For my full article (including pictures):

CORRECT AQUARIUM SILICONE APPLICATIONS (What Silicone to use and what not to use)-